Preheat the oven to 425 degrees Fahrenheit (218 degrees Celcius). Line a baking sheet with parchment paper. Set aside.
Add gluten-free flour blend, xanthan gum (if using), granulated sugar, baking powder, baking soda, and salt in a large bowl. Mix together with a fork.
Mix together the vanilla extract and heavy cream. Slowly add heavy cream mixture to the dry ingredients, mixing together with a fork. The dough should be scraggly with some dry spots.
Turn the dough out onto a floured surface. Knead the dough a few times just until it comes together, it should still be quite scraggly. Pat the dough or roll it out so that it is about ¾ inch thick. Cut into 8 circles using a biscuit cutter that is about 2.5-inches wide. You can also pat the dough into a rectangle and just cut the dough into squares if you prefer.
Place the dough rounds onto the parchment lined baking sheet, about 2 inches apart.
Brush the tops with heavy cream and sprinkle with turbinado sugar.
Bake at 425F for 16-18 minutes, until the biscuits are lightly browned. Do not over bake as the biscuits will get gritty and hard.
Remove from the oven and let cool before slicing down the center with a serrated knife.