Is it a cake? Or is it squares? You decide. Rhubarb Crumble Cake has components of both. The bottom layer tastes like a shortbread cookie covered with custardy rhubarb then topped with a crumbly mixture. There’s just a hint of cinnamon and it’s not too sweet.
I’ve heard from many people that they haven’t tried rhubarb. Which is surprising since you see so many patches growing randomly in back yards. Most of those people are happy to give it away. In fact that’s why I don’t grow rhubarb. I just steal it from some neighbours. Ok, I do ask permission and usually bring over a sample as a thank you. If you’re lucky, you too can score some for free.Jump to Recipe
Rhubarb Crumble Cake is based on a recipe I was given by a coworker years ago. She was a great baker and is actually the inspiration behind Strawberry Custard Cream Bars and Chocolate Chunky Monkey Loaf. She quickly wrote it down after giving us a sample one day. I tucked it away and just recently pulled it out. Apparently she forgot a few important components because something wasn’t right. So, after 3 versions it’s finally as good as I remember. Well, if I do say so myself, it’s better.
You’ll need about 4½ – 5 cups of chopped rhubarb so depending on the size of the stalks, plan for around 1 stalk per cup. If you’re stealing from a neighbour, carefully pull the stalks out from the root to promote new growth. If you cut them they don’t regrow. Just pull gently close to the bottom and twist if the stalks don’t come out easily. And don’t clean out the entire patch. Always leave at least 2/3 of the plant. Rhubarb is ready to harvest when the stalks are about 30 cm (1 foot) or more.
Give the rhubarb a good rinse and slice into small chunks. If the stalks are really thick, slice them lengthwise first. You can freeze chopped rhubarb too. Just dice it up and store in a freezer bag. Then if you get the urge to make a Rhubarb Custard Pie, you’re all set.
For Rhubarb Crumble Cake you need either an 8 or 9 inch baking pan. The smaller pan will give you a slightly higher finished cake but takes a bit longer to bake. There’s no need to butter the sides of the pan, the cake doesn’t tend to stick at all.
If you’ve got a food processor, use it to make the bottom layer. Just toss everything in and give it a whiz. Otherwise a pastry blender will work. The butter needs to be cold so it doesn’t melt until it hits the warm oven. Process it until there’s no larger lumps of butter. You might think the mixture looks a bit too dry but it’s supposed to be. Take out 1 cup of the mixture to save for the top of the cake.
Pour the remaining bottom mixture in the baking dish and spread it evenly. Press down gently but you don’t need to form it like you would a cheesecake base. Yes it looks like it’s going to be too dry but once baked, all the components of the recipe work together and magically morph into a moist and delicious cake.
You melt the butter in the next step. Then let it cool slightly while you make up the rest of the rhubarb mixture. Sift the flour, sugar and baking soda together and sprinkle over top of the chopped rhubarb in a large bowl. Whisk up the eggs and then whisk in the yogurt (or sour cream) and vanilla. Add it to the rhubarb mixture along with the melted butter and stir. Once it’s well blended, pour over top of the bottom layer and spread evenly.
Now take your reserved cup of the bottom layer, add some brown sugar and cinnamon and mix well. Sprinkle over top. The brown sugar is optional but it adds a little more sweetness to the cake and helps brown the top a bit.
Bake Rhubarb Crumble Cake for 45 minutes or about 50 if you’re using a smaller pan. Let it rest and cool slightly to help it stay intact for serving.
Here’s the recipe:
Rhubarb Crumble Cake
- 2 cups flour
- ½ cup sugar
- ½ cup cold unsalted butter
- pinch of salt
- 4½ - 5 cups chopped rhubarb
- ½ cup flour
- ½ cup sugar
- ½ tsp baking powder
- 2 eggs, beaten
- 1 tsp vanilla
- 1 Tbsp yogurt or sour cream
- ½ cup melted unsalted butter
- 1 cup reserved base mixture
- 1 Tbsp brown sugar optional
- ½ tsp cinnamon
- Preheat oven to 350° and set rack in middle of oven.
- Combine base ingredients in food processor or with pastry blender until fine crumbs. Remove 1 cup of mixture and reserve for top.
- Spread mixture in 9 inch square baking pan. Press gently and evenly.
- Sift flour, sugar and baking powder. Sprinkle over top of chopped rhubarb and mix well.
- Beat eggs. Whisk in yogurt and vanilla. Pour over rhubarb and mix.
- Melt butter. Allow to cool slightly. Add to rhubarb mixture and stir to combine. Pour rhubarb over cake base.
- Add brown sugar and cinnamon to reserved base mixture. Sprinkle evenly over top of cake.
- Bake for 45 minutes. If making 8 inch cake, bake for about 50 minutes or until a toothpick inserted in the centre of the cake comes out clean.