Mix Dry Ingredients: In a large bowl, whisk together flour, brown sugar, baking powder, baking soda, salt, and cinnamon. Break up any brown sugar clumps.
Combine Wet Ingredients: In a medium bowl, mix mashed bananas, melted butter, buttermilk, egg, and vanilla extract until well blended.
Create Batter: Pour wet ingredients into dry ingredients. Stir gently just until combined. The batter should be lumpy. Do not overmix.
Heat Griddle: Warm a griddle or large skillet over medium heat. Lightly brush with oil.
Cook Pancakes: Pour 1/4 cup batter onto hot griddle for each pancake. Cook until bubbles form on surface and edges look set, about 2-3 minutes. Flip and cook until golden brown, another 1-2 minutes.
Serve: Stack pancakes on plates. Top with sliced bananas, maple syrup, and chopped pecans.