Put the butter in a mug and microwave for 15 seconds. Tilt the glass a full 360 degrees so the butter coats the sides of the mug.
Add the egg, pumpkin puree and vanilla extract. Combine it with a fork.
Add the protein powder, pumpkin pie spice, baking powder, and erythitol and mix again with the fork combining thoroughly.
Microwave on high for 70-80 seconds, until done to your liking. Turn over onto a plate and enjoy immediately!
Note: The recipe calls for erythritol, but you can easily sub in 10 drops of liquid stevia if you don't want to use erythritol. Matt and I prefer stevia over erythritol!