Preheat oven to 350°F. In a large bowl, combine flour, baking soda and salt. This is the flour mixture. Set aside.
With a hand mixer or stand mixer fitted with a paddle attachment, beat butter until smooth and creamy.
Add sugar and beat for another minute, at medium speed. Scrape the sides and bottom of the stand mixer bowl to make sure everything is mixed evenly.
Add vanilla, then beat in 1 egg at a time. Mix in the mashed bananas (the mixture might curdle, that’s ok).
Add half of the dry ingredients and sour cream then mix. Repeat one more time and mix just until it comes together.
Spray the 12-cup bundt pan with no stick baking spray. Add the batter to the pan. Tap the pan on the counter a couple times (to remove air bubbles), then smooth out the top with a spatula.
Bake for 55-65 minutes, until a toothpick inserted into the center comes out clean.
Place the pan on a wire rack and gently push away the cake from its sides.
Invert it and leave it inside the cake pan. Let it cool for about 10 minutes in the pan. Then using an oven mitt, take out the pan gently, be careful not to disturb the shape of the cake.
PEANUT BUTTER FROSTING
In a stand mixer bowl, beat the butter on medium speed until creamy, about 2 minutes.
Add the peanut butter, confectioners’ sugar, heavy cream, vanilla extract, and salt while the mixer is on low.
Increase to high speed and beat for 3 full minutes. Add more confectioners’ sugar if frosting is too thin or another tablespoon of cream if frosting is too thick.
Decorate the cake with the frosting, fresh bananas and roasted peanuts.