Preheat oven to 375 degrees then spray a 7x5x2" baking pan (or similar size baking pan) with nonstick spray and set aside. Add peach slices, maple syrup, gluten-free flour, and cinnamon to a medium-sized bowl then mix with a spatula to combine. Scrape into prepared baking dish then set aside.
Add sugar and softened butter to the bowl then whisk until smooth, 30 seconds. Add egg white and vanilla then whisk until smooth. Add gluten free flour, baking powder, and salt then switch to a spatula and stir until the flour is just incorporated. Scoop the mixture evenly over the fruit then sprinkle with a little additional cinnamon and sugar.
Place baking pan on top of a baking sheet in case of overflow then bake for 22-26 minutes or until topping is light golden brown. Let cool for 10-15 minutes then scoop and serve with ice cream, if desired.
Notes
To easily peel peaches: score an "X" onto the bottom of the peaches then slide into a pot of boiling water for 30 seconds, or until peel starts to peel away. Let cool for a few minutes then peel and slice.