Preheat the oven to 350 degrees Fahrenheit and line a large cookie sheet with parchment paper.
Melt the butter (or coconut oil) in a microwave-safe mixing bowl. Whisk in the egg, pure maple syrup, and vanilla extract until creamy and the wet ingredients are well combined.
In a separate bowl, stir together the almond flour, tapioca flour (if adding), baking powder, baking soda, sea salt, and cinnamon until the dry ingredients are combined.
Pour the flour mixture into the mixing bowl with the wet mixture and stir until a thick dough forms.
Fold in the lemon zest (if adding) and the blueberries until they’re well-incorporated into the cookie dough.
Scoop mounds of dough onto the prepared baking sheet, making any size cookies you like. I make 9 large cookies and use a small cookie scoop to do so. Be sure to give the cookie dough balls have plenty of room to grow, as the dough will spread throughout the baking process. If you’d like, you can press extra blueberries into the tops of the dough (this is what I do).
Bake cookies on the center rack of the preheated oven for 8 to 12 minutes (I do 10), or until the edges are slightly golden brown and the centers have set up.
Remove the cookies from the oven and allow them to cool for 15 minutes before diving in! If you have a cooling rack, feel free to transfer the cookies to the wire rack after they have cooled for 15 minutes. This also helps prevent soggy bottoms.