This crumb cake is the offspring of three good cakes—Stella Moss’s Rhubarb Sheet, the Rhubarb Streusel Stella did for Judy Cornell of Conservation Grains, and Cheryl Norris’ Rhubarb Crumb Cake, which reset my standards for the right amount of crumb topping…a lot!
When creating my recipe, I decided to go for a square cake with abundant crumbly topping, one you can return to in every season. Choose seasonal, tart-leaning fruit, like rhubarb, rhubarb-strawberry, blueberries, sliced nectarines with some blueberries, and as we get into fall and winter, chopped apples perhaps studded with a few cranberries. If you have fruit compote or jam hanging around in the refrigerator, you can use some of that too.
Related recipes: Nectarine and Blueberry Cobbler, Galette, Peach and Blueberry Pie, Perfect Pie Crust, Oatmeal Crumble Berry Bars, Rhubarb purée from making simple syrup, and Strawberry Rhubarb Compote.
Rhubarb Crumb Cake
makes one 8 by 8-inch pan; adapted from Stella Moss's Rhubarb Streusel Cake for Conservation Grains
- ½ cup unsalted butter, softened to room temperature 113 grams; 1 stick
- ¾ cup brown sugar 125 grams
- 2 eggs
- ½ cup buttermilk
- ¾ cup all-purpose flour 106 grams
- ½ cup whole wheat flour 76 grams; Conservation Grains Wheatsome
- 1 teaspoon baking powder
- 1 lemon, zest from optional (I use either lemon zest or nutmeg, not both)
- ¼ teaspoon freshly grated nutmeg optional (I use either lemon zest or nutmeg)
- ¼ teaspoon Kosher salt
Fresh, Seasonal Fruit
- 2–4 tablespoons homemade fruit compote (rhubarb, strawberry-rhubarb, strawberry, or blackberry) optional
- 2 cups rhubarb, chopped ½-inch pieces about 1 pound, 4 stalks
- or use fresh or frozen blueberries with sliced nectarine
- or use chopped apple with fresh or frozen cranberries
- 6 tablespoons unsalted butter, melted 85 grams
- ½ cup sugar 109 grams; brown, or white, larger crystaled turbinado works great too
- ¾ cup flour (blend of all-purpose and whole wheat) 106 grams; 71 grams AP + 35 grams ww
- ½ teaspoon freshly grated nutmeg optional
- ½ teaspoon cinnamon optional
- 2 pinches Kosher salt
Preheat oven to 375°F. Grease 8 by 8-inch metal cake pan with melted butter, baking spray, or use parchment.
Cream butter and brown sugar using the paddle attachment in an electric mixer. Mix for a few minutes until color and texture is light.
Add eggs one at a time, mixing until fully incorporated before adding the next.
In a bowl, whisk together flours, baking powder, nutmeg or lemon zest, and salt. Add to the cake batter alternating with the buttermilk in 4 additions mixing until combined. Spread into prepared pan.
If using compote, spread over top of batter then scatter chopped rhubarb (or other fruit) over top.
Mix together in a bowl the flours, sugar, nutmeg, and salt. Drizzle over the melted butter and mix with a spatula until combined.
Crumble over the fruit layer then bake for 45 minutes to 1 hour depending on the moisture content of the fruit used. When approaching done, cake will be fragrant. When done, edges and topping will look dry vs. wet, color will be browning, and internal temperature will reach 200°F.