In a medium bowl, whisk together all dry ingredients (except sugar substitute and cinnamon) until well combined, set aside.
In a separate bowl - the bowl of a stand mixer fixed with a paddle attachment, or a large mixing bowl, if using an electric mixer - cream butter and sugar substitute until smooth and fluffy.
Be sure to scrape down the sides of the bowl a few times, to make sure everything is incorporated into the mix.
Add the eggs and vanilla extract to the mix, beating well to combine.
With mixer turned down to low speed, slowly add dry ingredients mix to the mixing bowl of wet ingredients, and carefully mix until well incorporated and smooth.
Wrap dough ball in plastic film, chill for 1 hour. This is an important step for any gluten free cookie dough, don’t skip it!
Preheat the oven to 350 F, line 2 baking sheets with parchment paper.
In a small bowl, combine remaining sugar substitute with the cinnamon, set aside.
Roll 1.25" balls out of the keto cookie dough, then roll in cinnamon mixture.
Arrange each dough ball on a lined baking sheet, leaving at least 2.5" between cookies - they flatten out a fair amount.
Gently press the tops of each - flatten JUST enough to prevent the dough from rolling.
Bake for 10-12 minutes. Cookies will look puffy, but flatten out as they cool. Do not overbake!
Allow cookies to cool for 2 minutes before removing from baking sheets.
Cool completely before storing in an airtight container.
Notes
Just over 9 grams of carbs per cookie come from sugar alcohols. Add that to the 1 gram of fiber, and you're left with just under 2 net grams of carbs per cookie!