Preheat your oven to 350°F. In a large, Swiss Diamond Nonstick Fry Pan over low heat, melt the butter. As the butter melts, in a large bowl, add the flour, sugar, cocoa powder, and baking soda. Mix well.
Then stir in the buttermilk, egg, vanilla, and the melted butter, leaving enough in the pan to lightly coat the surface.
Pour the batter into the pan and transfer to the oven. Bake until a toothpick inserted into the center emerges clean, about 30 minutes.
Wearing an oven mitt, carefully remove the pan and place it on a heatproof surface. Using a fish spatula, transfer the cake to a serving platter.
Top with peanut butter and banana slices.
Paul Kita is a food and nutrition editor at Men’s Health, the world’s largest lifestyle magazine. He is also the founder of MensHealth.com’s popular food and cooking blog, Guy Gourmet. In 2013, Kita cowrote Guy Gourmet: Great Chefs’ Amazing Meals for a Lean & Healthy Body and 2017’s A Man, A Pan, A Plan. Kita is a James Beard Award winner, and has appeared on the Travel Channel and numerous national radio and broadcast stations.