Preheat the oven to 350℉ and spray a 9x13-inch baking dish with cooking spray or line the dish with parchment paper. Set aside.

Place the bananas in a large bowl and mash until smooth. Add the rest of the wet ingredients to the bowl and mix using a hand mixer. Set aside.

In a separate bowl, whisk together the dry ingredients. Mix the dry ingredients with the wet ingredients until they are completely combined.

Transfer the batter to the baking dish and bake for 40 minutes. Remove from the oven and allow at least 3 hours to cool completely.

While the cake is baking, prepare the frosting. Add the butter, cream cheese, peanut butter, and vanilla extract to a bowl. Using a hand mixer, beat together the ingredients until completely combined. Add in the powdered sugar and blend until smooth. Refrigerate until ready to frost.

Allow the frosting to sit at room temperature for 10-15 minutes before frosting the cake. Spread on top of the cake and serve.