In a food processor, pulse the gluten-free flour, almond flour (if using), sugar, and salt to combine. Add the cold, cubed butter and pulse until the mixture resembles coarse crumbs.

1. Slowly add the ice water, one tablespoon at a time, until the dough starts to come together. Be careful not to add too much water — the dough should be crumbly but able to hold together when pressed.
2. Turn the dough out onto a lightly floured surface and knead it just a few times to bring it together. Form it into a disk, wrap it in plastic wrap, and refrigerate for at least 30 minutes.
3. In a medium bowl, combine the halved cherries, sugar, cornstarch, lemon juice, vanilla extract, and a pinch of salt. Stir until the cherries are evenly coated and the mixture thickens slightly. Set aside.
4. Preheat your oven to 375°F (190°C) and line a baking sheet with parchment paper.
5. Roll out the chilled dough on a floured surface to about 1/4-inch thickness. Cut the dough into 4-6 circles, depending on the size you want for your galettes.
6. Place a few tablespoons of the cherry filling in the center of each dough circle, leaving about a 1-inch border around the edges.
7. Gently fold the edges of the dough over the filling, pleating as you go, to create a rustic edge. Brush the exposed dough with the beaten egg wash (or almond milk) and sprinkle with sugar if desired.
8. Bake the galettes in the preheated oven for 30-35 minutes, or until the crust is golden brown and the filling is bubbling.
9. Allow the galettes to cool for a few minutes before serving. Enjoy warm, with a scoop of vanilla ice cream or a dollop of whipped cream.