Preheat your oven to 350 degrees, and grease and flour a 9-inch loaf pan, preferably with straight sides. Set aside. 

In a medium bowl, whisk together the flour, almond flour, salt, baking soda, and cinnamon. Set aside. 

In a large bowl, beat together the butter, brown sugar, and sugar until combined and fluffy. Add in the egg, mashed bananas, and vanilla extract and beat until combined. 

Add in the flour mixture and the buttermilk in alternating additions, starting and ending with the flour mixture, and beat until completely incorporated. Pour the batter into your prepared pan. Bake for 50-55 minutes, or until a cake tester comes out clean. 

Cool the cake in the pan for 15 minutes, and then turn out onto plastic wrap. It's okay if the cake is still pretty warm. Wrap the cake tightly, and freeze for at least an hour before slicing and frosting. 

In a large bowl, beat together the butter and peanut butter until fluffy. Slowly beat in the powdered sugar and salt, scraping the bowl when needed. The mixture will be thick. Add in the heavy cream, and beat until fluffy. 

To build your cake, unwrap the frozen cake, and slice it in half with a sharp knife. On the bottom half, spread a generous portion of frosting, and sprinkle on the chopped peanuts. Top with the second half, and frost and decorate as desired. Enjoy!