Rhubarb cakes have a quiet charm. They don’t try to impress with layers or frosting — they win you over with balance. This one leans into the contrast: deep brown sugar sweetness against pockets of tart rhubarb, finished with a cinnamon-sugar topping that melts gently into the surface as it bakes. It’s the kind of cake that feels right in a simple pan, sliced generously, and served warm or cold without ceremony.
Ingredients
Cake Batter
- 1 1/3 cups brown sugar, packed
- 1/2 cup margarine or unsalted butter, softened
- 1 large egg, room temperature
- 1 teaspoon vanilla extract
- 1 cup buttermilk
- 2 cups all-purpose flour
- 1 teaspoon baking soda
- 1/2 teaspoon salt
- 2 cups rhubarb, chopped into small pieces
Topping
2 tablespoons butter, cut into small pieces
1/3 cup granulated sugar
1 teaspoon ground cinnamon
Instructions
- Preheat the oven to 350°F. Lightly grease a 9×13-inch baking pan.
- In a large bowl, cream together the brown sugar and margarine until smooth and creamy. Beat in the egg, followed by the vanilla extract.
- In a separate bowl, whisk together the flour, baking soda, and salt.
- Add the dry ingredients to the sugar mixture in two additions, alternating with the buttermilk. Mix just until combined — do not overmix.
- Gently fold in the chopped rhubarb, distributing it evenly throughout the batter.
- Spread the batter evenly in the prepared pan.
- In a small bowl, mix the granulated sugar and cinnamon. Sprinkle evenly over the top of the batter, then dot with small pieces of butter.
- Bake for 30–35 minutes, or until a toothpick inserted in the center comes out clean.
- Cool slightly before slicing. Serve warm or at room temperature.
Baker’s Note
This cake becomes even softer by the next day. It’s excellent on its own, but a spoon of lightly sweetened whipped cream or vanilla yogurt pairs beautifully with the tart rhubarb.
