Preheat the oven to 180C/350F degrees
Whisk the butter and erythritol until blended.
Add the vanilla extract and the eggs, one at a time and continue to whisk.
Add the coconut flour, protein powder, baking powder and salt. Whisk until smooth.
If the mixture is too thick, add a tablespoon or two of water until the consistency is smooth.
Chop the strawberries into small pieces
Add the strawberries into the muffin mixture and stir evenly.
Line a muffin tin with 9 cupcake cases.
Spoon the muffin batter into the muffin tin.
Bake for 35-40 minutes until the cupcakes are firm
Remove from the oven and set aside to cool