Preheat oven to 350 degrees F (176 C) and line two baking sheets with parchment paper. Set aside.
Prepare the coating for later by adding coconut sugar or organic cane sugar and cinnamon to a small bowl and mixing to combine. Set aside.
Add softened butter of choice to a large mixing bowl and beat until creamy and smooth — about 1 minute.
Add sugar of choice and mix on medium speed until fluffy and light — about 1 minute. Then add chickpea brine (aquafaba, or other egg substitute) and vanilla and mix again, scraping down sides as needed.
Add baking powder, cream of tartar (optional), ground cinnamon, and sea salt, and blend to combine. Then add gluten-free flour blend, almond flour, and cornstarch or arrowroot and stir with a wooden spoon until the ingredients are combined.
The dough should be thick and almost difficult to mix at this point. If too soft, add 1 Tbsp gluten-free flour blend and almond flour at a time until a thick, moldable dough is formed. Then cover and transfer dough to the refrigerator. Optional: Chill dough for 30 minutes, which helps yield a slightly more well-formed cookie (we tested it both ways and both work well).
Use a cookie scooper (like this one) or Tablespoon to measure out 1 ½ Tbsp amounts of dough to gently roll into balls. The dough will still be soft, so be gentle. Roll in the cinnamon-sugar topping and arrange on the parchment-lined baking sheets. Press down gently with the palm of your hand or a glass to smash slightly.
Bake for 10-12 minutes, or until slightly golden brown and expanded (some cracks are normal — they won't expand a ton). Remove from the oven and let cool on a baking sheet for 10 minutes. Then enjoy!
Once cooled, store leftover cookies covered at room temperature for 3-4 days, or in the freezer up to 1 month.
*1 package of Miyokos is equivalent to 2 sticks of butter. If using Miyokos, use 1/2 package (as original recipe is written // adjust if altering batch size). *If cutting back on sugar with stevia, this will make the cookies softer, so you will likely need to add more gluten-free flour, almond flour, and/or cornstarch to help thicken the dough — adjust as needed. *We tried testing this recipe with aquafaba, pumpkin purée, and an egg and much preferred the aquafaba. Although an egg and pumpkin purée did work, just didn't produce as good of texture / flavor! *Cream of tartar provides the snickerdoodle cookies with that quintessential tanginess. However, it is not an essential ingredient in this recipe. *We tested this recipe with our DIY gluten-free flour blend and can’t guarantee the results of other store-bought or homemade mixes. *If not gluten-free, you can try subbing the gluten-free flour blend with unbleached all-purpose flour, but we haven’t tested it this way and can’t guarantee good results. We would recommend adding less as it's drier and more absorbent. *You can make the cookie dough ahead of time and refrigerate up to 2-3 days in advance. Simply let the dough rest at room temperature for 30 minutes before scooping and baking. It should be soft and moldable.