Preheat oven to 350F and line an 8x8 inch baking dish with parchment paper.
In a mixing bowl, combine the gluten free all-purpose flour, granulated sugar, and baking powder.
Cut the cold unsalted butter into pieces and blend into the dry ingredients using a pastry blender. Stir in the egg and vanilla extract until a crumbly dough forms.
Press two-thirds of the dough firmly into the bottom of the prepared baking dish to form a crust.
Spread the cherry pie filling evenly over the bottom crust.
Crumble the remaining dough over the top of the cherry layer. Bake for 35-40 minutes until the top is lightly golden brown.
Let the bars cool. Whisk the powdered sugar and milk together to create a simple glaze, drizzle over the top, and cut into squares.