Melt butter in a microwave-safe mug or ramekin. Then add vanilla extract and the egg. Whisk until yolk is incorporated and mixture is well-combined.
In a small bowl, combine coconut flour, Swerve, and baking powder. Mix thoroughly to combine.
Add dry ingredients to the mug (or ramekin), then mix thoroughly until well-combined.
Fold in the blueberries.
Place the mug in the microwave for one minute on high.
When finished, put a fork in the mug cake and carefully lift it up and flip it over. If the bottom isn’t fully cooked yet (this will depend on your microwave), cook it for another few seconds.
Top with desired toppings (see the Notes section for a delicious glaze icing) and enjoy!
Notes
Optional glaze icing: Mix 1 1/2 tbsp Swerve Confectioners and 1 tsp unsweetened almond or coconut milk.
If you're dairy-free, you can use coconut oil instead of butter in this recipe.