Step 1

Preheat oven to 350°F. Grease an 8-inch square baking pan.

Step 2

Whisk together the flour, baking powder, salt, and baking soda. Set aside.

Step 3

In a separate bowl, combine the cooled butter, brown sugar, egg, and vanilla until thoroughly combined.

Step 4

Add the flour mixture, mixing just until combined. Mix in the bananas.

Step 5

Transfer the batter to the prepared pan and spread evenly.

Step 6

Dollop the dulce de leche over the top of the batter. Use a thin knife to swirl the dulce de leche into the batter. (Alternatively, you can mix it into the batter before transferring to the pan.)

Step 7

Bake 35 to 40 minutes, or until a pick inserted into the center comes out clean.

Step 8

Cool in the pan before cutting into bars.