Preheat your oven to 350°F (175°C). Prepare two 9-inch round cake pans by greasing them with butter and lightly dusting with flour.

Toast 1 cup of chopped walnuts in a dry skillet over medium heat for 3-4 minutes until fragrant.

In a large mixing bowl, whisk together 2 cups of flour, 2 teaspoons of baking powder, 1 teaspoon of baking soda, and a pinch of salt.

In another bowl, beat 3/4 cup of softened butter with 1 cup of granulated sugar until light and fluffy.

Add in 3 large eggs, one at a time, then mix in 1 teaspoon of vanilla extract.

Add 1 1/2 cups of mashed bananas and 1/2 cup of buttermilk, mixing until just combined.

Gradually add the dry mixture to the banana batter, alternating with toasted walnuts.

Divide the batter between prepared cake pans and bake for 30-35 minutes until golden brown.

Allow cakes to cool in pans for 10 minutes, then transfer to a wire rack.

Prepare banana filling by tossing sliced bananas with lemon juice. Whip 1 cup of heavy cream with 2 tablespoons of powdered sugar until stiff peaks form.

Once the cake layers are cool, place one layer on a serving plate, spread whipped cream, add a layer of banana filling, and top with the second layer.

Frost the top and sides with remaining whipped cream, chill for at least 1 hour before serving.