This rhubarb cake recipe is one of our favorite desserts for how it combines tart rhubarb and a touch of brown sugar to create a light, airy cake with a delicious rhubarb filling. At times this rhubarb cake recipe can seem a little fussy because it has a few different components; but don't worry, in the end, they come together to create a delicious cake that you'll make again and again.
Start by combining the flour, cinnamon, baking soda, and salt. In a small bowl mix the milk and lemon juice. In another bowl whisk the egg and vanilla extract together.
Using a mixer, cream the butter and brown sugar. Start adding the wet and dry ingredients to the mixer, alternating between wet and dry.
Once the flour, egg, and milk mixtures have been incorporated, take the bowl off the mixer and fold in 2 cups of finely diced rhubarb.
Streusel Topping
In a small bowl mix the butter, flour, brown sugar, and cinnamon together.
Rhubarb Filling
In a small saucepan, cook the rhubarb, sugar, and cinnamon with 1/4 cup of water on a low simmer. Stir occasionally, until the rhubarb has broken down and thickened up.
It usually takes 15 to 20 minutes for the rhubarb filling to thicken. The filling is done when it has a jam like consistency.
We usually make the rhubarb filling while the cakes are baking, but it can be made ahead of time.
Baking
Split the cake batter between two greased 8-inch cake pans. Sprinkle the streusel topping on both cakes and bake in a 350℉ oven for 30 to 35 minutes.
Let the cakes cool before covering one with rhubarb filling and putting the other one on top.