In a large bowl, whisk together the almond flour, coconut flour, granulated sweetener, baking powder, xanthan gum, and salt.

Add the cubed softened cream cheese and cold butter to the dry ingredients.

Using a pastry blender or a fork, cut the fats into the flour mixture until it looks like a coarse, crumbly meal with small pea-sized bits of butter left throughout.

In a separate small bowl, whisk together the egg and vanilla extract.

Pour the egg mixture into the flour and fat mixture. Stir gently with a spatula until a thick, cohesive dough forms.

Gently fold in the blueberries, taking care not to burst them too much.

Turn the dough out onto a piece of parchment paper. Pat and shape it into a flat disk about 6 to 7 inches wide and 3/4-inch thick.

Using a sharp chef's knife or a bench scraper, slice the disk into 6 or 8 equal triangles.

Separate the triangles slightly on the parchment-lined baking sheet so air can circulate.

Bake for 15 to 18 minutes, or until the edges are golden brown and the tops are firm to the touch.

Let them cool on the baking sheet for 10–15 minutes (cream cheese doughs are delicate when piping hot), then transfer to a wire rack.