Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans, or line them with parchment paper for easy removal.
In a medium bowl, whisk together the all-purpose flour, baking soda, and salt. Set aside.
In a large mixing bowl, beat the softened butter, vegetable oil, granulated sugar, and brown sugar together until light and fluffy. This should take about 3-5 minutes with an electric mixer.
Add the eggs one at a time, mixing well after each addition. Then stir in the mashed bananas and lemon juice until fully incorporated.
Gradually add the dry ingredients to the banana mixture, alternating with the buttermilk. Start and end with the dry ingredients, mixing until just combined.
Divide the batter evenly between the prepared cake pans. Bake in the preheated oven for 25-30 minutes or until a toothpick inserted into the center comes out clean.
Once baked, remove the cakes from the oven and allow them to cool in the pans for about 10 minutes. Then, transfer them to a cooling rack to cool completely.
In a mixing bowl, beat the cream cheese and unsalted butter together until smooth. Gradually add the powdered sugar and vanilla extract, mixing until the frosting is fluffy and well combined.
Once the cakes are completely cool, place one layer on a serving plate. Spread a generous amount of cream cheese frosting on top, then place the second layer on top and frost the top and sides of the cake.
