Shuffle the flour, baking powder, sea salt, and cinnamon through a sieve into a medium bowl. Set aside.
Beat together the butter, coconut sugar and natural peanut butter using either a stand mixer fitted with the paddle attachment, a hand mixer, or a wooden spoon and some elbow grease until the ingredients are creamy and slightly fluffy.
Crack in the egg, pour in the vanilla, and combine well.
Add the dry ingredients to the wet ingredients in two portions, mixing only until each portion is incorporated and the flour disappears. The dough will appear quite wet – this is completely normal. Cover the dough bowl with foil and refrigerate overnight for best results. If necessary, chill the dough for a minimum of 6 hours.
Once the dough has chilled, preheat the oven to 170°C and prepare a cookie sheet with a silicone baking mat or baking paper.
Using a cookie scoop or tablespoon, measure out and roll 2-inch sized balls of dough and place them evenly spaced on the cookie sheet. Using a fork dipped in flour, press the dough balls down to flatten them slightly and create the traditional peanut butter cookie pattern.
Bake the cookies for 9-11 minutes; they should be golden brown on the bottom and just up the edges of each cookie. Allow the cookies to cool on the tray for 5 minutes, then move them to a wire rack to finish cooling.