Preheat your oven to 350°F (180°C) and line a muffin tin with paper liners.
In a large bowl, whisk together almond flour, coconut flour, Erythritol baking powder, baking soda, and salt.
In a separate bowl, beat the eggs and then add almond milk, melted coconut oil, and vanilla extract. Mix well.
Combine the wet and dry ingredients, stirring until just combined.
To make the cinnamon swirl take a small bowl and mix the Erythritol and ground cinnamon for the swirl.
Melt the butter and add it to the sweetener-cinnamon mixture. Stir until well combined.
Assemble the muffins by spooning the muffin batter evenly into the prepared muffin tin.
Drizzle the cinnamon swirl mixture over each muffin.
Use a toothpick or a knife to swirl the cinnamon mixture into the batter.
Bake in the preheated oven for about 18-20 minutes or until a toothpick inserted into the center comes out clean.
Allow the muffins to cool in the tin for a few minutes before transferring them to a wire rack to cool completely.