This rhubarb raspberry upside-down cake has a few raspberries tucked into the rhubarb fruit layer to enhance the colour of pink rhubarb while also lending lots of flavour and sweetness to this dessert
What is an upside-down cake?
Upside-down cakes are traditionally made with rings of canned pineapple and pink maraschino cherries to add a pop of colour and sweetness to the retro, classic fruit dessert. That makes it particularly easy to bake this type of cake year round because you can always find canned pineapple at the grocery stores, and maraschino cherries too, regardless of the season.
The fruit is baked on the bottom of the cake pan, underneath the cake batter. Once baked, the cake is flipped onto a serving plate to reveal the fruit layer that was hidden under the cake. This is how this dessert gets its name.
Upside-down cakes are known for being very decorative because you can take time to arrange the fruit in a pattern which bakes into the cake, anchoring the fruit in place.
The upside-down cake recipe is a perfect example of a classic recipe that you can tweak to suit the seasons with the fresh local fruit at the market. You can imagine using summer berries mid-summer, or sliced peaches or nectarines in the late summer months. And in the spring and early summer, replacing the canned pineapple with flavourful stalks of rhubarb is ideal!
Some varieties of rhubarb are pink and sweet. Others are more green and sour. Early spring rhubarb and forced rhubarb are bright pink or red, sweeter and more tender, while late summer rhubarb is more green and very tart.
Cooking and baking with rhubarb that is more green than pink can be a little disappointing because it turns into a beige-green colour that isn't quite what you'd expect when you think of rhubarb. That's where sneaking in some sweet pink raspberries or bright red summer strawberries can make your best rhubarb recipes even better, adding lots of sweetness to balance out the tart rhubarb, and also tons of vibrant colour to enhance those stalks of rhubarb that are more green than red.
Updates to this recipe
The original rhubarb upside-down cake recipe first appeared in the New York Times and I started baking this rhubarb raspberry version in 2011. I've since converted it to metric weights so now you have both in the recipe below. I also did a little tweaking:
- For colour and sweetness, I replaced part of the rhubarb with raspberries for the rhubarb layer
- For the cake layer, instead of cake flour, I used a combination of all-purpose, lightened with ground almond. I replaced 60 grams (½ cup) of the flour with 50 grams (½ cup) ground almond
The cake batter is a variation on the pound cake recipe, also called a quatre quarts (which is the French baking term for the pound cake). The pound cake is made with roughly equal weights of flour, butter, sugar, and eggs.
The original recipe calls for cake flour, which is a softer, finer flour that has more starch and less protein than all-purpose or bread flours. Baking with cake flour leads to a more tender cake with is why many favour this baking ingredient. Where I live, cake flour is hard to find, so that's why I replaced it with all-purpose, which is more readily available. But instead of replacing one with the other, cup-for-cup, I replaced a portion of it with ground almonds for flavour and to lighten the texture of the cake layer and so that less gluten forms when the batter is mixed.
Baking upside-down cakes: Tips & tricks
Upside-down cakes are not hard to make, but when you are baking them, there are things you need to know to successfully make one, especially if you want to bake an upside-down cake with fresh or frozen fruit.
Before baking prep the pan
Upside-down cakes are baked in a springform pan because the sides of this pan are taller and so can accommodate a taller cake made from fruit and cake batter. Given the cake is baked with a thick layer of fruit and sugar on the bottom and because the cake is flipped to unmould and serve it, it's very important to properly prepare the cake pan before baking:
- Line the bottom of the pan with parchment, which is naturally non-stick
- Butter the sides of the pan as well as the parchment, again to ensure the cake doesn't stick and unmoulds cleanly
Leaky springform pans
Another issue you may run into, your springform might be too leaky to contain the syrupy sweet fruit juices that form as the cake bakes. Springforms are notorious for this reason and I have yet to work with a pan that doesn't leak, regardless of price point.
It's imperative that you wrap the springform with two layers of durable aluminum foil. This way, you won't need to place it on a sheet pan. And if the pan leaks, the juices aren't lost, they won't burn on the bottom of your oven, and you can simply pour them over the cake after you unmould it.
The fruit layer
You'll notice for the fruit layer in this recipe, we incorporate a little cornstarch. With canned pineapple, you probably won't see that because canned pineapple has less moisture. Remember rhubarb has a ton of water trapped inside and as the fruit cooks, it breaks down, releasing all that water. That's why we need to add cornstarch for this version of the upside-down cake: to gel the water so that the fruit layer is less soupy.
Getting the cake to bake properly
All upside-down cakes pose a unique challenge because of the fruit layer on the bottom of the cake pan: this fruit layer insulates the bottom of the cake, slowing the baking of the cake significantly. Furthermore, most upside-down cakes are quite thick and tall, and that depth increases the baking time even more.
For these reasons, baking upside-down cakes all the way to the centre can be tricky. You have to make sure that the part of the cake that is adjacent to the fruit layer is baked, and for this cake, it takes at least 1 hour 45 minutes to properly bake a 9-inch diameter cake that is so tall. If you aren't careful, you may end up with a wet, gummy, or raw cake in the middle!
You can't cool the cake completely in the springform because we need to be able to unmould it: otherwise, the cake will adhere to the sides of the pan, and the fruit syrup will set and stick to the parchment if the cake gets too cold.
For this reason, you can only cool the cake briefly in the pan, just long enough to be able to handle it. Fifteen minutes is all you need to wait before flipping it onto a serving plate:
- let the hot cake cool 15 minutes before un-moulding
- run a knife along the edge between the edges of the cake and the sides of the pan to loosen it
- place a large plate over the pan
- place your left palm flat under the cake pan and place your right palm flat on top of the plate to hold them together
- flip swiftly holding, maintaining the pressure of your palms on the plate and the pan. Don't hesitate just do it!
- lift the pan upwards slowly and gently to release it OR unlock the buckle of the springform to release the sides, then carefully peel to springform base off the fruit layer
If any fruit stick to the parchment, don't panic! Just transfer them back where they belong!
With upside-down cakes, it's important to take the time to melt the sugar for the fruit layer, which helps reduce sugar crystallization when the cake is baked. The thing to note is that your brown sugar quick caramel may crystallize in the pan, while you prepare the rest of the cake. If this happens, don't panic. The cake takes so long to bake and with the fruit juices, the caramel will dissolve because both the rhubarb and the raspberries have a lot of water.
On the other hand, for a pineapple upside-down cake, you may have to take extra steps to prevent crystallization because the fruit isn't as juicy. A squeeze of lemon juice added to the brown sugar mixture when it's on the stove can help too, as can a spoonful of honey, both of which help prevent crystallization of sugar syrups.
If you don't have sour cream, a baking substitution you can try is to replace it with the same volume of full-fat Greek yogurt (around 10 % fat if possible). Low-fat works too, but the reduction in fat may lead to a dryer cake or have an impact on texture..
Rhubarb raspberry upside-down cake
For the quick caramel sauce
- 58 grams (¼ cup) unsalted butter
- 100 grams (½ cup) light brown sugar
For the fruit layer
- 450 grams (1 lb) fresh rhubarb cut into pieces to help them fit the springform from about ½ to 4 inches
- 170 grams (1¼ cups) fresh raspberries or frozen
- 100 grams (½ cup) granulated sugar
- 10 mL (2 tsp) cornstarch
For the cake layer
- 190 grams (1½ cups) all-purpose flour
- 50 grams (½ cup) ground almonds
- 6.25 mL (1¼ tsp) baking powder
- 0.625 mL (⅛ tsp) Diamond Crystal fine kosher salt
- 230 grams (1 cup) unsalted butter room temperature
- 250 grams (1¼ cups) granulated sugar
- 5 mL (1 tsp) pure vanilla extract
- 4 large eggs room temperature
- 80 mL (⅓ cup) sour cream (14% fat) or full-fat Greek yogurt
- Preheat the oven to 325°F.
- Prepare a 9-inch springform pan by lining the bottom with parchment (I basically cut a large square of paper, place it on the base, then clip the sides over so that the paper runs right through the springform). Butter the paper and the sides of the springform pan. Wrap the outside of the pan with 2 large sheets of aluminum foil (in case your springform is as leaky as mine is). Set aside.
Make the quick caramel sauce
- In a small saucepan, melt the butter and brown sugar until it gets bubbly. Let it bubble for about 2 minutes, stirring constantly.
- Pull the pan off the heat and pour the mixture into the bottom of the prepared pan. Smooth it out so that it forms an even layer. Set aside.
Prepare the fruit
- In a medium bowl, combine the fruit with the granulated sugar and cornstarch. Mix it carefully to not damage the raspberries too much, and let it sit. Stir the fruit every few minutes to evenly distribute the starch and sugar.
Make the cake batter
- Whisk together the flour, ground almonds, baking powder, and salt in a medium bowl. Set them aside.
- In the bowl of an electric mixer fitted with the paddle attachment, cream the butter and the granulated sugar.
- Add the vanilla, and then the eggs, one at a time, beating well, and scraping down the sides of the bowl after each addition. Don’t worry if the batter looks curdled at this point.
- Alternately, add the dry ingredients (one-third at a time) and the yoghurt (half at a time), beginning and ending with the dry ingredients. Be sure to scrape down the sides and the bottom of the bowl occasionally.
Assemble the upside-down cake and bake
- Arrange the fruits evenly on top of the sugar layer (either decoratively or just neatly arrange them to fit snuggly). Pour the juices over the fruit.
- Dollop the cake batter carefully over the fruit being sure to smooth the top without disturbing the fruit layer. Bang the pan on the counter so as to remove any air pockets (you could also swirl a knife through carefully to remove any air pockets, just be sure to avoid the fruits at the bottom).
- Bake for 1 hour 40 minutes to 1 hour 50 minutes, until a cake tester inserted into the centre of the cake comes out clean. Because the cake is tall, it takes a long time to bake the middle so make sure you bake it for long enough!
- Let the cake cool for 15 minutes in the pan, then place your serving plate over top, and flip it very carefully because the fruit juices are boiling hot! Set the plate on a wire rack to cool completely. Do not let the cake cool in the pan because the fruits and juices will stick to the bottom, and you’ll have a hard time getting it out after.