1. Preheat oven to 350 degrees. Line standard muffin tins with paper liners. Whisk dry ingredients in a large bowl. Mash bananas, buttermilk and vanilla in a separate bowl. Cream butter and brown sugar with a mixer until light and fluffy. Add eggs, 1 at a time, beating after each addition.
2. Reduce speed to low. Add dry ingredients to butter mixture in 3 additions, alternating with wet ingredients and ending with dry. Scrape sides of bowl. Mix pecans in by hand. Divide batter among muffin cups, filling each 2/3 full.
3. Bake cupcakes until testers inserted into centers come out clean, about 20 minutes. Let cool in tins on wire racks.
4. Once cupcakes are cool, frost tops with caramel buttercream. Frosted cupcakes will keep, covered and refrigerated, for up to 2 days. Top with banana slices before serving.

These would be great just eaten as muffins without any frosting, but who wants to skip the caramel frosting? It really is the best part.