- Mix coconut flour, golden flaxseed meal, gluten-free baking powder, and sea salt in a mug.
- Add the egg and melted coconut oil. Stir well, until smooth, making sure no dry ingredients are left at the bottom. Let sit for a minute to thicken.
- Optional step: Depending on your coconut flour, if the batter is very stiff, you can thin it out with water or milk of choice (unsweetened almond milk, coconut milk beverage, or heavy cream are all low carb options). If you do this, add the liquid a teaspoon at a time until thin enough. It should be easy to stir, but not liquid; the amount will depend on your brand of coconut flour.
- In a small bowl, combine the remaining erythritol and cinnamon. Place the cinnamon mixture in a heap in the center of the mug on top of the batter, then use a spoon to swirl just a couple of times. (Don't over-stir to keep the marble effect.) Level the top with the back of a spoon.
- Microwave on high for 1 to 2 minutes, until set. (If you prefer to use the oven, bake in an oven-safe ramekin at 350 degrees F (177 degrees C) for 10-20 minutes, depending on the shape of your ramekin.)