Prep the basics: Line two baking sheets with parchment. Set the oven to 350°F (175°C).
Make sure butter and egg are at room temperature.
Cream the fats and sugars: In a large bowl, beat butter, almond butter, granulated sugar, and brown sugar until light and fluffy, about 2 minutes.
Add the egg and flavor: Mix in the egg, vanilla, and almond extract (if using) until smooth.
Combine dry ingredients: In a separate bowl, whisk the gluten-free flour, cornstarch, baking powder, baking soda, and salt.
Bring it together: Add dry ingredients to wet and mix on low until just combined. The dough should be soft but not sticky.
Chill: Cover and refrigerate for 30–45 minutes. This helps the cookies keep their shape and improves texture.
Form and coat: Scoop dough into 1 1/2-tablespoon balls.
Roll each in granulated sugar and place on the baking sheets, leaving about 2 inches between cookies.
Bake: Bake 9–11 minutes, until edges are set and tops are slightly cracked. The centers should look just a bit underdone.
Cool: Let cookies rest on the sheet for 5 minutes, then transfer to a wire rack to cool completely.