In a measuring cup or mug, stir together the almond flour, sugar-free sweetener and sea salt until combined. Add the coconut oil and egg yolk and stir until a thick cookie dough forms.

In a separate small bowl, stir together 1 teaspoon of sugar-free sweetener with ⅛ teaspoon of ground cinnamon. Note: this makes enough topping for 2 snickerdoodle mug cookies...I use these measurements to get the ratio of sweetener to cinnamon just right :)

Smooth the cookie dough into an even layer and sprinkle with desired amount of the cinnamon and sugar mixture.

Microwave on high for 30 to 60 seconds (I do 40), until cookie is cooked through but still slightly gooey.