Add all ingredients except food coloring into an oversized microwave safe mug. Mix with a whisk until batter is smooth. Add in one drop of food coloring. Using a fork, gently swirl in a circular clockwise motion until red swirls form, but stopping before cake batter turns completely red.
Cook in the microwave for about 1 minute or until done. The cake is a bit plain, so I recommend that you serve it with whipped cream, Cool Whip, or a chocolate drizzle.
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.