Preheat the oven to 375 degrees F. Grease a 24-cup mini muffin pan with nonstick spray.
In a medium bowl, stir together the flour, cinnamon, if using, baking powder, baking soda, and salt.
In another bowl, stir together the banana, yogurt, butter, eggs, and vanilla.
Gently stir the yogurt mixture into the flour mixture.
Divide batter among the prepared muffin tin, using about 2 tablespoons batter in each cup. It will fill about to the edge. (To make standard size muffins, use ¼ cup batter.)
Bake for 10-12 minutes, or until the edges are lightly golden brown and a cake tester inserted into the center comes out cleanly. Remove from oven, then transfer muffins to a wire rack to cool fully. (To bake standard size muffins, bake for 14-16 minutes.)
Notes
Once cooled, store in an airtight container for up to 3 days at room temperature. Store in the fridge in an airtight container for up to 5 days. Warm slightly to serve from the fridge (they firm up a bit when they're cold so warming slightly returns them to their softer texture).
You can also freeze the muffins in a freezer bag with as much air removed as possible for up to 3 months. Thaw at room temperature or in 15 second increments in the microwave.
Use one optional add-in (such as chocolate chips, blueberries or strawberries) per batch of muffins, or use 1 tablespoon of each per muffin to make a mixed batch.
Add 1/4 cup sugar to the batter to enhance the sweetness of the muffins if desired.
Dairy-free: Use a nondairy Greek style yogurt like the plant-based options from Siggis and a neutral oil like canola in place of the butter.
Gluten-free: Substitute cup-for-cup gluten-free flour in place of the wheat flours.
Egg-free: Omit the eggs. Reduce the yogurt to 1/4 cup. Add 1/4 cup milk. Proceed with the recipe.