Preheat the oven to 180°C/350°F and line a muffin tin with paper liners.
Whisk together the almond flour, vanilla protein powder, erythritol, and baking powder in a large bowl.
In a separate bowl, whisk together the melted butter, eggs, orange zest, and orange juice.
Pour the wet ingredients into the dry ingredients and stir until well combined.
Divide the batter into muffin tin, filling each cup almost full. There should be enough batter for 6 cups.
Bake for 22-25 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Remove the muffins from the oven and allow them to cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.