Preheat the oven to 350°F (175°C). Grease and line two 8-inch round cake pans with parchment paper.

For the banana cake, cream together the butter and sugar in a large bowl until light and fluffy.

Add the eggs, one at a time, beating well after each addition. Stir in the vanilla extract.

In a separate bowl, whisk together the flour, baking powder, baking soda, and salt.

Add the dry ingredients to the butter mixture alternately with the buttermilk, beginning and ending with the dry ingredients. Mix until just combined.

Fold in the mashed bananas and chopped pecans (if using).

Divide the batter evenly between the prepared cake pans and smooth the tops.

Bake for 40-45 minutes, or until a toothpick inserted into the center comes out clean.

Let the cakes cool in the pans for 10 minutes, then transfer them to a wire rack to cool completely.

For the caramel sauce, melt the butter in a saucepan over medium heat. Stir in the brown sugar, heavy cream, vanilla extract, and salt.

Bring the mixture to a simmer, stirring constantly, and cook for 3-5 minutes until thickened. Remove from heat and allow to cool slightly.

For the frosting, beat the softened butter in a bowl until smooth and creamy. Gradually add the powdered sugar, heavy cream, and vanilla extract. Continue to beat until the frosting is light and fluffy.

To assemble the cake, place one layer of banana cake on a serving platter. Drizzle with a little caramel sauce and spread a layer of frosting over the top.

Place the second layer of cake on top and frost the entire cake with the remaining frosting.

Drizzle the remaining caramel sauce over the top of the cake and garnish with chopped pecans.

Allow the cake to set for 15-20 minutes before serving.