Nana's Banana Cake with Salted Caramel Buttercream

1. For the cake: Preheat the oven to 350 degrees F. Prepare three 8-inch cake pans with baking spray and parchment liners.
2. Using a stand mixer with a paddle attachment, cream together the granulated sugar, light brown sugar and butter on medium-high speed until light and fluffy. Slowly add the eggs, one at a time, mixing each fully before adding the next.
3. With the mixer on low, slowly trickle the oil into the mixture. Once added, increase the speed to medium-high and continue to mix until the mixture thickens and begins to look like mayonnaise. Using a silicone spatula, scrape down your bowl, making sure to get anything at the bottom of the bowl that has not been mixed well.
4. In a small bowl, combine the buttermilk and vanilla extract. In a medium bowl, sift together the flour, baking powder, baking soda, cinnamon and salt. Add a third of the flour mixture to the butter mixture and beat on medium high speed for 90 seconds. Bring the speed down to low and, alternately, add the buttermilk mixture and remaining flour mixture in 4 stages, beginning with the buttermilk mixture and ending with the flour mixture. Fold in the mashed bananas. Mix only enough to incorporate the ingredients after each addition.
5. Pour the batter into the prepared pans, filling two-thirds full. Bake until a toothpick inserted into the center comes out clean, 35 to 40 minutes. The top of the cake should spring back slightly after a gentle tap with your finger. Allow to cool for 10 to 15 minutes before removing from the pans. Allow the cakes to cool completely before frosting.
6. For the salted caramel Swiss meringue buttercream: Using a stand mixer with a paddle attachment, beat the egg whites and confectioners' sugar on medium-high until the mixture thickens to fluffy white, 3 to 4 minutes. Reduce speed to medium and gradually add the softened butter. Increase the speed to medium-high and continue mixing for 5 to 7 minutes. Reduce the speed and add the prepared caramel sauce, vanilla and salt. Mix until combined.
7. To assemble the cake: Frost the top of 1 cake round with some salted caramel Swiss meringue buttercream. Drizzle with some prepared caramel sauce and sprinkle with some pecans. Add a second round and repeat with the buttercream, caramel sauce and pecans. Top with the remaining cake round and frost the entire cake with the buttercream. 

Homemade Salted Caramel Sauce

1. Combine the sugar, corn syrup and 1/4 cup water in a saucepan, making sure the sugar is completely wet, but being careful not to let the sugar water coat the sides of the pan. Turn the heat to medium-high and cook for about 4 minutes. The cooking process is done when the sugar has reached a nice amber color. Do not stir during the cooking process. Quickly remove the sugar from the heat and add the heavy cream. The mixture will bubble. Stir to combine. Whisk in the butter, sea salt and lemon juice. Allow to cool completely before use.