Preheat the oven to 425 degrees F. Prepare a muffin tin by lining with paper liners or spraying with nonstick baking spray. Set aside.
Whisk together the almond flour, GF flour, sugar, salt, and baking powder in a large bowl, making sure no lumps remain. In a separate medium bowl, whisk together the eggs, milk, vanilla, and lemon zest. Slowly whisk in the melted butter. Add the egg mixture to the flour mixture and thoroughly combine. Toss the blueberries in an additional teaspoon of the gluten-free flour, then gently stir them into the batter.
Fill muffin cups almost full (I use a heaping 1/4 cup scoop) and bake for 18-20 minutes, rotating the pan halfway through. The muffins are done when they are golden brown and the top springs back when lightly touched with a finger. A toothpick inserted in the center will come out with moist crumbs.
Tip out onto a cooling rack immediately and cool completely before storing. The muffins are best the day they are baked, but will keep in an airtight container at room temperature for up to a week (they will become a bit dry after a day or two) or will keep in the freezer for up to 3 months.