Make the Crust Dough:

1. Whisk dry ingredients: In a medium mixing bowl, whisk together the gluten-free flour, almond flour, granulated sugar, and salt.
2. Grate in butter: Use the large-hole side of a cheese grater to grate in the cold butter. Gently toss in with your hands to coat the butter in the flour, making sure there are no large chunks. 
3. Add liquid ingredients: Add 5 ounces ice water, vanilla extract, and almond extract. Use a spatula to fold in the liquid ingredients until the dough begins to come together. Use your hands to finish bringing the mixture together into a single ball of dough, adding the remaining 1 ounce ice water as needed. Be careful not to overwork the dough.
4. Chill dough: Cover dough with plastic wrap and transfer to the refrigerator to chill for 45 minutes.

Prep the Filling: 

1. Combine filling ingredients: In a clean, medium mixing bowl, combine 3 ⅜ cups finely chopped rhubarb, 3 cups finely chopped strawberries, 1 cup + 1 Tbsp. granulated sugar, ¼ cup cornstarch, 1 ½ tsp. lemon juice, and 1 ½ tsp. vanilla extract, tossing together gently until evenly combined. Refrigerate until ready to use, straining out any excess juice before using.

Assemble and Bake:

1. Prep rolling surface: Cut two piece of parchment paper sized to fit a full-size cookie sheet. Dust each generously with flour. 
2. Portion and roll dough*: Divide the chilled dough into 6 equal portions. Working with one portion at a time and keeping the rest refrigerated, dust top with flour and roll out into a 6” round. Repeat with three more portions of dough so you have four crusts rolled out on a single piece of parchment. Roll out the final 2 portions of dough on the second piece of parchment. 
3. Trim dough: Use a paring knife to trim the outer border of each crust so the edges are clean. Use the leftover scraps to roll out one final crust on the second piece of parchment. Carefully lift or slide each piece of parchment onto a cookie sheet.
4. Add filling: Spread 2 tsps. almond flour over each crust, leaving about a ½” border around the perimeter. Divide the filling evenly over the almond flour on each galette. Finish by folding the edges of the crust over the outer border of fruit filling. 
5. Preheat oven: Transfer both baking sheets to the refrigerator to chill for about 15 minutes. Meanwhile, preheat oven to 400ºF with oven racks in the bottom and top-third positions.
6. Glaze: Just before baking, combine 2 Tbsp. melted, salted butter and 1 large egg in a small bowl, and whisk until smooth. Brush over the crust on each galette and sprinkle generously with raw sugar. 
7. Bake: Bake galettes in preheated oven for 25-30 minutes, until crusts are golden. Serve warm, with whipped cream or ice cream.