Ingredients
For the cake
- 1 1/2 cups all-purpose flour
- 1 teaspoon baking powder
- 1/2 teaspoon baking soda
- 1/4 teaspoon salt
- 1/2 cup unsalted butter, softened
- 1 cup granulated sugar
- 2 large eggs
- 1 cup mashed ripe bananas (about 2–3 bananas)
- 1/2 cup sour cream
- 1 teaspoon vanilla extract
For the crumb topping
- 1/2 cup all-purpose flour
- 1/2 cup packed brown sugar
- 1/4 cup unsalted butter, cold and cubed
- 1 teaspoon ground cinnamon
Prep Time: 15 minutes | Cooking Time: 45–50 minutes | Total Time: 65 minutes
Servings: 8 | Approx. 320 kcal per serving.
Step‑by‑step instructions
Step 1: Prep the pan and oven
Preheat the oven to 350°F (175°C). Grease and flour a 9‑inch round or square cake pan, tapping out any excess flour. Lining the bottom with parchment after greasing makes it even easier to release the cake, especially with the crumb topping.
Step 2: Mix the dry ingredients
In a medium bowl, whisk together the 1 1/2 cups flour, baking powder, baking soda, and salt until well combined. Set aside. Whisking first helps distribute the leaveners evenly so the cake rises uniformly.
Step 3: Cream butter and sugar
In a large bowl, cream the softened unsalted butter and granulated sugar together until light and fluffy. This usually takes 2–3 minutes with a hand mixer and helps incorporate air into the batter for a softer crumb.
Step 4: Add eggs, bananas, sour cream, and vanilla
Add the eggs one at a time, beating well after each addition until fully incorporated. Mix in the mashed ripe bananas, sour cream, and vanilla extract until the mixture is smooth and uniform. The batter will look creamy and slightly thick. Using very ripe bananas (with lots of brown spots) boosts both sweetness and banana flavor.
Step 5: Combine wet and dry ingredients
Gradually add the dry flour mixture to the wet ingredients, mixing on low speed or with a spatula just until incorporated and no dry streaks remain. Avoid over‑mixing at this stage to keep the cake tender rather than tough.
Step 6: Make the crumb topping
In a separate bowl, combine the 1/2 cup flour, brown sugar, and ground cinnamon. Add the cold, cubed butter and cut it into the dry mixture using a pastry cutter, fork, or your fingers until the mixture resembles coarse crumbs with pea‑sized pieces of butter. Keeping the butter cold helps the topping bake up crisp and crumbly.
Step 7: Assemble and bake
Pour the banana cake batter into the prepared pan and spread it evenly to the edges. Sprinkle the crumb topping evenly over the surface of the batter, covering it from corner to corner.
Bake for 45–50 minutes, or until the top is golden and a toothpick inserted into the center comes out clean or with just a few moist crumbs (no wet batter). If the crumb topping starts to brown too quickly toward the end, you can tent the cake loosely with foil.
Step 8: Cool and serve
Let the cake cool in the pan on a wire rack for about 15 minutes to set the structure. Then, if you lined the bottom with parchment and want to unmold it, carefully run a knife around the edges and lift or invert gently; otherwise, you can leave it in the pan and slice directly from there. Allow it to cool completely before slicing for the cleanest pieces.