Mix all the ingredients together into an oversized mug using a fork or small whisk until batter is smooth. Cook in microwave for about 1 min 30 seconds. It might need an additional 30 seconds. Be careful not to overcook as batter will become dense and rubbery.
Let cake cool slightly before piping frosting. For frosting, combine all ingredients into a mixing bowl and mix on high speed until light and fluffy. Pipe onto cake.
The nutrition information provided are only estimates based on an online nutritional calculator. This is not a comprehensive list of all the nutrients in the recipe (i.e., does not include vitamins, cholesterol, etc). I am not a certified nutritionist. Please consult a nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.