Preheat oven to 400 degrees & prepare your muffin tins. Set aside.
Cream butter & sugar in large mixer bowl.
Add egg & bananas- mix well.
Mix flour, baking powder & salt in small bowl. Set aside.
Mix cinnamon & sugar in a small bowl & transfer to bowl with apples. Stir to coat apples.
Add flour mixture & milk to butter mixture & beat on medium speed until well combined.
Add vanilla- beat in.
Fold in apples.
Spoon batter into prepared muffin pans (this made 34 muffins)
Combine additional cinnamon & sugar & sprinkle on top of each muffin before baking (optional)
Bake for 20 minutes.
Remove & cool on wire rack 10 minutes.
Store in airtight container for up to 4 days.