In a large bowl, whisk together the flour, baking powder, sugar and salt.
In a separate medium bowl, whisk together the milk, eggs, vanilla extract and sour cream. Add the wet ingredients to the dry ingredients and fold them together with a spatula. (Do not overmix the batter. It should be lumpy.)
Heat a large nonstick skillet or griddle pan over medium-low heat. Add 1 tablespoon of butter and once it has melted, scoop 1/4 cup of the batter into the pan. Top the pancake with sliced bananas. Once bubbles form across the pancake, flip it once and continue cooking until it's cooked through. Repeat the cooking process with the remaining batter.
Serve the pancakes topped with sliced bananas and maple syrup.