A recipe for a rhubarb pudding cake: a rhubarb compote on the bottom with a vanilla cake baked on the top. Serve warm with a scoop of vanilla ice cream!
In a medium pot, stir together the sugar and cornstarch with a wooden spoon. Add the chopped rhubarb and toss to coat then heat on medium to release the juices from the fruit, and to thicken the compote, stirring constantly.
When the compote has simmered for at least 5 minutes and the mixture is thickened significantly, take the pot off the heat.
Divide the mixture among 6 ramekins and set them aside while you make the cake batter.
To make the buckwheat cake
Preheat the oven to 350 °F (175 °C). Whisk together the flours, baking powder and salt in a bowl, and set this aside.
In the bowl of an electric mixer fitted with the paddle attachment, cream the butter and the sugar for 3 minutes.
Add the egg and vanilla and beat well until the batter is smooth.
Add the dry ingredients alternately with the milk, beating the batter just until smooth and all the ingredients are incorporated.
Top the ramekins of compote with the cake batter and bake for about 30 minutes or until a cake tester inserted into the center of the cake layer comes out clean.