Preheat oven to 350F degrees. Spray muffin tray with cooking spray. Set aside.
In a large bowl, stir to combine the flour, sugars, baking soda, & cinnamon. Slice the banana in half and mash 1st half with a fork and cut 2nd half into thin slices (set these aside).
Add the mashed banana to the dry ingredients and stir.
Add the applesauce, beaten egg white, vanilla and stir until just combined. Do NOT overmix.
Gently fold in the strawberries and banana slices. Pour batter into muffin tray, filling about 2/3 of the way up. Bake for 15 minutes, or until a toothpick inserted in the middle comes out clean.
Muffins stay fresh and soft up to 7 days in an airtight container. Muffins freeze well.