Spray an 8x8-inch square glass baking pan with Baker's Release spray and set aside.
Combine flour, baking powder and salt in a small bowl.
Slice the firm banana and place in a small bowl with the lemon juice (to prevent discoloration).
In another bowl, mix the granulated sugar, cooled melted butter, egg, vanilla and mashed banana until smooth, then fold in the sliced banana (with the lemon juice as well) and the chopped strawberries.
Add the dry flour mixture and stir just until moist and incorporated.
Spread the batter in the pan sprayed with Baker's release.
Mix the topping ingredients until crumbly and sprinkle over the batter.
Bake for 35-40 minutes or until you can insert and remove a toothpick without wet batter clinging to it.
Cool in pan15 minutes, then turn out and complete cooling on a wire rack.
Stir together the drizzle and spoon lightly over the cooled coffee cake.