Preheat the oven to 375 degrees F. Spray a 12-cup muffin tin with cooking spray.
Line a plate with 2 layers of paper towels and place the cherries on top to dry briefly.
Put the bananas in a large bowl and mash them very thoroughly with a fork. Add the vanilla and mix and mash to combine. Add the eggs and whisk until well beaten.
Divide the cherries evenly among the muffin cups, then pour in the banana custard (each cup will be about three-quarters full). Bake until the muffins are domed and set, 12 to 14 minutes.
Run a thin knife around the edge of each muffin and remove with a small offset spatula. Cool slightly. Dust with powdered sugar if using and serve.