While best served warm, this cake can be made a day ahead and reheated.
2 3/4 cups all-purpose flour, divided
1 cup granulated sugar
1 1/2 teaspoons baking powder
1/2 teaspoon baking soda
1/2 teaspoon salt
1 cup cold unsalted butter, cut into pieces and divided
2 large eggs
1 cup mashed banana
1/2 cup sour cream
1 tablespoon vanilla extract
1/4 cup firmly packed light brown sugar
1 cup pecan pieces
1 (13.4-ounce) can dulce de leche (we tested with Nestlé)*
How to Make It
Combine 2 1/4 cups flour and next 4 ingredients in a large bowl. Cut 3/4 cup butter into flour mixture with a pastry blender until crumbly. Whisk together eggs and next 3 ingredients; add to flour mixture, stirring just until dry ingredients are moistened.
Spread batter into a greased 13" x 9" pan.
Combine remaining 1/2 cup flour and brown sugar in a small bowl. Cut remaining 1/4 cup butter into flour mixture with pastry blender. Add pecans, pressing streusel mixture between fingers until large clumps form. Sprinkle streusel over batter in pan.
Microwave dulce de leche in a small glass bowl on HIGH 1 minute or until drizzling consistency, stirring once; drizzle over streusel topping.
Bake at 350° for 35 to 38 minutes or until streusel topping begins to brown and center of cake puffs slightly. Cool slightly.
*Find dulce de leche in the ethnic section or on the baking aisle of your grocery store.