Preheat your oven to 350°F (175°C) and grease two 9-inch round cake pans with butter or cooking spray and dust with flour.

In a medium bowl, combine 2 cups of all-purpose flour, 1 teaspoon of baking soda, and ½ teaspoon of salt. Whisk together until uniform.

In a large mixing bowl, beat ¾ cup of softened unsalted butter with 1 cup of granulated sugar for about 3-5 minutes until light and fluffy.

Add 2 large eggs one at a time, mixing well after each addition until fully incorporated.

Mix in ½ cup of sour cream and 2 teaspoons of pure vanilla extract until just blended.

Mash 3 ripe bananas in a separate bowl and fold them into the wet mixture until fully incorporated.

Gradually add the dry flour mixture to the wet ingredients, mixing on low speed until just combined.

Fold in 1 cup of chopped walnuts with a spatula.

Divide the batter evenly between the prepared cake pans and smooth the tops. Bake for 35-40 minutes.

Once baked, cool the cakes in the pans for 10 minutes then invert onto wire racks to cool completely.

Place one layer of cake on a serving plate, spread a layer of vanilla custard filling between the layers, and drizzle remaining custard on top.

Decorate with sliced bananas and additional chopped walnuts, brushing banana slices with lemon juice to prevent browning.