01 - Preheat the oven to 350°F. Lightly grease a 12-cavity donut pan with cooking spray or butter.
02 - In a large bowl, mash the ripe bananas until smooth. Whisk in melted butter and brown sugar until thoroughly combined.
03 - Add eggs, milk, and vanilla extract to the banana mixture. Whisk until the mixture is smooth and uniform.
04 - In a separate bowl, whisk together flour, baking powder, baking soda, cinnamon, nutmeg, and salt until well distributed.
05 - Gradually fold the dry ingredients into the wet mixture until just combined. Avoid overmixing to prevent dense donuts.
06 - Spoon or pipe the batter evenly into the prepared donut cavities, filling each about 3/4 full to allow for rising.
07 - Bake for 10-12 minutes until a toothpick inserted into the center comes out clean and donuts are golden brown.
08 - Let donuts cool in the pan for 5 minutes, then carefully transfer to a wire rack to cool completely before glazing.
09 - In a small bowl, whisk powdered sugar with 1-2 tablespoons milk and vanilla until smooth. Drizzle or dip cooled donuts.