Preheat your oven to 350°F (175°C) and line a muffin tin with parchment paper liners.
In a large mixing bowl, whisk together the eggs, melted coconut oil, and vanilla extract until well combined.
Scoop out the flesh of the ripe avocados and add them to the mixing bowl. Use a fork or a potato masher to blend until smooth and creamy.
In a separate bowl, combine the coconut flour, cocoa powder, sweetener, baking powder, and cinnamon. Gradually incorporate this dry mixture into the wet ingredients, stirring until just combined.
Gently fold the chopped dark chocolate (or sugar-free chocolate chips) into the batter, ensuring even distribution.
Divide the batter evenly among the prepared muffin cups, filling each about two-thirds full.
Bake in the preheated oven for 18-20 minutes or until a toothpick inserted into the center comes out clean.
Allow the cupcakes to cool in the tin for about 10 minutes before transferring them to a wire rack to cool completely. Enjoy them as is or with your favorite keto-friendly frosting!