Preheat oven to 350°F (180°C).

In a large bowl, whisk together flaxseed, almond flour, erythritol, baking powder, salt, nutmeg, and cinnamon.

Add beaten eggs and melted butter to the dry mixture and stir until fully combined. If the batter is too thick, add about 1/4 cup water to loosen it.

Spoon the batter into a muffin tin lined with paper or silicone cups, filling each just over halfway.

Bake for 20–25 minutes, or until the tops are golden brown and a toothpick comes out clean.

Let muffins cool in the pan for a few minutes before transferring to a wire rack.

For the optional topping, mix melted butter with cinnamon and dip the muffin tops into the mixture before serving.