1 cup white sugar
½ cup butter, softened
6 ripe bananas, mashed
2 eggs, beaten
1 ½ cups cake flour
3 tablespoons cake flour
1 teaspoon baking soda
½ teaspoon salt
½ teaspoon vanilla extract
½ cup European cookie spread (such as Biscoff®)
Preheat oven to 350 degrees F (175 degrees C). Grease a loaf pan with cooking spray. Combine sugar and butter in a large bowl; beat with an electric mixer until creamy. Beat in bananas and eggs. Mix 1 1/2 cup plus 3 tablespoons cake flour, baking soda, and salt together in a bowl. Mix into the banana mixture. Stir in vanilla extract. Pour half of the batter into the prepared pan. Heat cookie spread in the microwave until softened, about 20 seconds. Spread over the batter in the pan. Cover with remaining banana batter; swirl decoratively with a knife. Bake in the preheated oven until a toothpick inserted into the center comes out clean, 50 to 60 minutes. Cool in the pan for 5 minutes. Invert onto a wire rack. Cool for 10 to 15 minutes before serving.