Mash banana with a fork or in a blender. Add eggs, cinnamon, baking powder, salt, and vanilla. Mix until combined and has the consistency of batter.
Heat a skillet over medium-high heat with butter. When the pan is hot, spoon the batter into the pan to the size of the desired pancake – up to about 4" (10 cm) in diameter is easiest to flip.
Before flipping, and while the batter is still runny on top, sprinkle some berries onto the pancake.
When bubbles appear on the top of the pancake, flip it over and fry until golden on the underside as well.
Serve the hot pancakes with a dollop of butter.