- 3/4 cup butter, room temperature, divided
- 1/2 cup plus 1/3 cup packed brown sugar, divided
- 2 tablespoons heavy cream
- 1 tablespoon plus 1 1/2 teaspoons dark rum, divided
- 1/2 teaspoon vanilla
- 3 large bananas, halved lengthwise
- 1/2 cup granulated sugar
- 2 eggs
- 1 3/4 cups all-purpose flour
- 1 1/2 teaspoons baking powder
- 3/4 teaspoon fine sea salt
- 1/4 teaspoon cinnamon
- 3/4 cup milk
- 1/2 cup finely chopped walnuts
- 1/4 cup sour cream
- Heat oven to 350F. Spray bottom and sides of a 9-inch square pan with cooking spray.
- In a medium saucepan over medium-high heat, melt 1/4 cup butter. Stir in 1/3 cup brown sugar and heavy cream; bring to a boil. Stir in 1 tablespoon rum and vanilla; cook for 1 minute. Pour mixture into prepared pan. Arrange halved bananas cut side-down on top of syrup mixture in bottom of pan.
- In a large bowl with an electric hand mixer or in the bowl of a stand mixer with the paddle attachment, beat granulated sugar, 1/2 cup brown sugar and 1/2 cup butter on medium speed 3-4 minutes until fluffy and smooth. Stir in eggs, one at a time, then stir in 1 1/2 teaspoons rum.
- In a separate medium bowl, whisk flour, baking powder, salt and cinnamon until well combined. With mixer on low speed, add flour mixture to butter mixture alternately with milk, beginning and ending with flour mixture, beating until just combined after each addition. Gently stir in walnuts and sour cream. Pour and spread batter over bananas in pan.
- Bake 50-55 minutes until a toothpick inserted in the center of the cake comes out clean. Cool cake in pan 10 minutes. Top cake pan with parchment paper and an upside-down cooling rack; carefully but quickly invert cake pan onto paper-topped rack. Remove pan to reveal cake. Cool completely before slicing.
- Store covered tightly in a refrigerator for up to 3 days.