Prep: Preheat oven to 375ºF (190ºC). Line a muffin tin with paper or foil liners.
Mash & Mix: In a large Ziploc bag, mash bananas. Add eggs, seal, and shake until combined. Add sugar and mix again.
Dry Ingredients: Add flour, salt, baking soda, baking powder, and cinnamon to the bag. Briefly stir them together at the top of the bag with a spoon before sealing and mixing fully.
Wet Ingredients: Add oil and vanilla. Seal and squish until the batter is smooth.
Pipe: Snip a small corner of the bag. Gently squeeze the batter into the muffin liners, filling about 3/4 full.
Bake: Bake for 20 minutes or until a toothpick comes out clean.
Glaze: If desired, whisk glaze ingredients together and drizzle over cooled muffins.