This rhubarb crumble recipe is so easy and creates a tart, perfectly set rhubarb filling topped with an oat-free crumble topping.
When it's peak rhubarb season, I love to bake recipes that feature rhubarb on its own so this tart ingredient can shine, whether that's in a small batch rhubarb jam or a rhubarb pie without strawberries. These recipes and this rhubarb crisp without oats allow the tart flavour of rhubarb to dominate.
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Crisp Versus Crumble
The naming of desserts with fruit is confusing: there are crisps, crumbles, cobblers, grunts, and the list goes on.
Though a crisp meant a base of fruit topped with a crumbly oat topping, whereas a crumble had no oats, nowadays, the two names are used interchangeably. I'm calling this a rhubarb crumble, but in your household, maybe you'd call it a rhubarb crisp. Either way, it's delicious!
Ingredients
This easy recipe calls for a very short list of ingredients. If you've got rhubarb, then you probably have everything else in your pantry to make this easy rhubarb dessert!
- rhubarb—use fresh rhubarb if you can (trimmed and washed thoroughly) but frozen will also work
- sugar—I used granulated sugar for the filling, but light brown sugar would also be nice, adding a little flavour to the filling
- thickener—I prefer cornstarch as a thickener with rhubarb because of the water it releases
- vanilla—either vanilla bean paste or pure vanilla extract
- flour—you can use any type of flour for the crumble topping. I used bleached all-purpose flour
- salt—Diamond Crystal fine kosher salt
- butter—unsalted butter cold and cut into cubes
- raspberries are very much optional in this recipe: I add them to rhubarb fillings to enhance the pink colour if the rhubarb is very green
Please see the recipe card for the exact ingredients and quantities.
Thickeners for Rhubarb Desserts
Rhubarb has a lot of water, more than you would think when you look at it and cut into it. This means, if you don't add enough thickener to it, the juices will create a soupy filling that is difficult to serve and quite watery.
You need to incorporate a thickener in rhubarb fillings in order to thicken the juices and gel them so that the filling is jammy and set, not watery and overly loose.
- Flour is an easy choice, but flour creates a filling that is more opaque and white-ish. Flour is also not as potent as other thickeners, so you may have to use a lot more, which will then interfere with the flavour of rhubarb desserts.
- Starches like cornstarch, tapioca starch, or minute tapioca are preferable for desserts with rhubarb. All of these thickeners create a rhubarb filling that is set, clear, and vibrant in colour and taste.
Oat-free: Not every crumble topping has to have oats in it and the toppings can vary quite a bit. Many people prefer them without! This cherry crumble is topped with a crumble made with cocoa powder. This grape crisp has oats and peanut butter in the crumble topping. This mango crisp has sliced almonds in the topping.
Variations and Substitutions
If you want to bake a fruit crumble without a thickener, try these strawberry rhubarb crumbles. Baked in smaller ramekins, the smaller volume of filling has a better chance of heating up and bubbling, and the strawberries contribute a certain amount of pectin to help gel the fruit layer.
Some bakers use the crumble topping as a thickener, stirring a portion of it into the filling instead of flour or cornstarch. This is another option you can consider, but I have never tried it.
Tips for Achieving the Perfect Set
- use enough thickener for the amount of fruit you are baking: for 2 pounds of fruit in the filling, in order for the thickener to do its job, you need to make sure the fruit filling, from edge to centre, bubbles and boils.
- bring it to a boil: if you don't ensure the middle of the fruit layer is bubbling, the filling just won't gel without enough heat. Trust me. I tested shorter baking times and the results were mediocre.
- let the crumble or crisp cool down completely for several hours, if not overnight, before serving. This gives enough time for the filling to gel.
I photographed this rhubarb crumble the day it was baked, about an hour later so it was still warm and a little more fluid, but by the next morning, the filling was completely set.
Tip: Make this dessert the day before to give it ample time to set, then reheat it just before serving to warm it up!
How to Make a Rhubarb Crumble
Step 1: Combine half the chopped rhubarb with the sugar and thickener in your 8x8 or 9x9 baking dish. Roast it to release some of the water, which will help evenly disperse the sugar and thickener.
Step 2: Once all the sugar is dissolved and the water has been released from the partially baked rhubarb, I add the rest of the fruit (and a couple of raspberries if needed to enhance the pink colour).
Step 3: Prepare the crumble topping by combining the dry ingredients with cold butter so it has a coarse uneven texture.
Step 4: Top the fruit with an even layer of crumble from edge to edge. Use it all!
Note: The temperature of the butter has an impact on the texture of the crumble topping:
- Make a crumble topping with cold butter and keep it cold so that the mixture is finer, more powdery and dry.
- Make a crumble topping with softened butter (room-temperature butter) OR work in the cold butter for longer until it warms up and softens. This will give you a crumble topping with the texture of cookie dough that holds together well and has larger clumps.
Bake the rhubarb dessert until the filling is bubbling in the middle and the topping is golden brown all over.
Top Tip: Baking in two stages
For fruits that contain a lot of water, like blueberries and rhubarb, I prefer to bake crumbles and crisps in two stages, a trick I learned from Stella Parks.
- Bake half the fruit with the sugar and thickener to get the juices flowing and to get the thickener hydrated.
- Mix in the rest of the fruit and top with the crumble topping to finish baking.
With this method, the filling has a mixture of soft jammy fruit with pieces of fruit that hold their shape. It's the best of both worlds.
Baking in two stages also allows you to give the filling a better chance of cooking properly so that the juices gel. It also gives you a chance to stir the filling a little more, part way through the baking process, so that you know the sugar is dissolved and evenly dispersed, as well as the thickener.
This is a technique I used for the blueberry rhubarb crisp because otherwise, the filling was too loose and the crumble topping would burn before the filling came to a boil when I tried to bake them together in one step.
Serving Suggestions
I love to serve warm fruit crumbles and crisps with plain vanilla ice cream, this cardamom ice cream or even this lemon custard ice cream, but you can also serve them with sweetened whipped cream or vanilla bean crème anglaise (custard sauce).
Rhubarb Baking FAQs
Some rhubarb varieties are greener than others. If you are really looking for a pinker hue for your baked goods, tuck in a few raspberries with the rhubarb (even just a handful will suffice). The raspberries will break down as the filling bakes and stain the rhubarb filling pink. Nobody will know your secret! Strawberries also work, but they have more of a presence even when baked, so I prefer raspberries if you are just looking for a pop of colour.
I like to use a ratio of butter to dry ingredients (flour/oats) where I use roughly three times more dry ingredients than butter by volume, so I use 1-½ cups flour (190 grams) for ½ cup butter (115 grams).
More Rhubarb Recipes
If you love to bake with rhubarb as much as I do, you will love these other rhubarb recipes:
If you tried this recipe for the best rhubarb crumble (or any other recipe on my website), please leave a ⭐ star rating and let me know how it went in the comments below. I love hearing from you!
📖 Recipe
Rhubarb Crumble
Equipment
Ingredients
Rhubarb filling
- 1 kg fresh rhubarb trimmed and washed thoroughly
- 250 grams granulated sugar
- 32 grams cornstarch
- 30 mL water
- 5 mL vanilla bean paste or pure vanilla extract
- 10 Fresh raspberries optional (adds pink colour if your rhubarb is very green)
Crumble topping
- 185 grams bleached all-purpose flour
- 100 grams granulated sugar
- 1.25 mL Diamond Crystal fine kosher salt
- 115 grams unsalted butter cold and cut into cubes
Optional
- Vanilla bean ice cream for serving
Instructions
Rhubarb filling
- Preheat the oven to 400 ºF (200 °C). Place a 8x8x2 inch (20x20x5 cm) ceramic baking dish (like a deep square Pyrex or a ceramic baking dish with at least 2 inch sides) on a parchment-lined sheet pan. Set aside.
- Slice washed rhubarb into 1 inch (2.5 cm) pieces. Place half the rhubarb in the baking dish. Sprinkle the sugar, cornstarch, and water over top, then toss the ingredients together to evenly coat all the rhubarb. You can use your hands for this.
- Cover the baking dish with a sheet of aluminum foil then bake the rhubarb for 30 minutes. When you carefully peel back the foil, you will see the rhubarb should be soft and has released a lot of water.
- Fold in the rest of the rhubarb and the vanilla bean paste (or extract) to make sure the filling is well mixed using a heatproof spatula. You can also add a few raspberries for colour. Set aside.
Crumble topping
- Drop the oven temperature to 375 ºF (190 °C).
- In a large bowl, whisk the flour, sugar, and salt.
- Drop the cubes of butter into the bowl and using your hands toss them in the flour mixture to coat them. Work the butter into the flour using your finger tips to form a crumbly mixture.
- Sprinkle the crumble over the rhubarb filling. Bake the rhubarb crumble, uncovered, until the filling is bubbling and very hot, even in the middle, and the topping is golden. This will take about an hour, if not more.
- Let cool for at least an hour (if not several hours) so that the juices set. Serve plain or topped with vanilla ice cream.
Video
Notes
- The raspberries are optional. We add them to make sure our rhubarb filling is bright pink, especially when rhubarb is green. You can skip them or replace them with strawberries.
- Two-stage baking process: We do this to ensure the sugar and thickener are evenly dispersed throughout the fruit layer, to avoid any clumping that can occur, and to achieve the perfect set:
- Bake half the fruit with the sugar and thickener to get the juices flowing and to get the thickener hydrated.
- Mix in the rest of the fruit and top with the crumble topping to finish baking.
- Serving suggestions: I love to serve warm fruit crumbles and crisps with plain vanilla ice cream, this cardamom ice cream or even this lemon custard ice cream, but you can also serve them with sweetened whipped cream or vanilla bean crème anglaise (custard sauce).
- Tip: Make this dessert the day before to give it ample time to set, then reheat it just before serving to warm it up!
Ina Patience says
I have lots of frozen rhubarb. Could I use it to make this crisp? If so, any different steps? I am presuming it must be defrosted and drained first. It is all weighed out in bags..
Thank you.
HappyBaker says
This looks wonderful! My garden rhubarb is ready to be picked, so thanks for the post! Can you recommend a gluten free topping? Thanks too for the tip on two-stage baking—I am going to give it a try!
Janice says
Hi, I'd replace the flour with a cup-for-cup gluten-free blend that you usually bake with!