Preheat the oven to 350 degrees F. Prepare three 9-inch cake pans; rub the inside with butter and dust with flour. Cut a piece of parchment paper to fit inside and put on the bottom of the cake pan.
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.
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, scraping the sides occasionally.
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.
Pour the batter into the prepared pans. Bake until a toothpick inserted into the center comes out clean, 25 to 35 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.
To Make the Frosting:
Beat first 4 ingredients at medium speed with an electric mixer until creamy.
Gradually add powdered sugar alternately with 3 Tbsp. milk, beating at low speed until blended and smooth after each addition.
Drizzle caramel sauce into buttercream and beat on low speed to combine.
To Make the Salted Caramel: (or use a purchased product and add finishing salt to taste)
Combine the sugar, corn syrup and 1/4 cup water in a large, deep 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 vigorously; stir to combine.
Whisk in the butter and sea salt. Allow to cool completely before use. Yield: approximately 2 cups
To assemble the cake:
Frost the top of 1 cake round with some salted caramel 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 and finish with more caramel sauce and pecans.
I decided to frost mine with a 'bare' look but you don't have to follow suit. Just frost as you regularly would and finish with the pecans and caramel drizzle.