Combine all ingredients except lime zest into an oversized microwave-safe mug. Mix with a small whisk until batter is smooth. Stir in lime zest.
Cook in the microwave for about 1 minute. Let cake cool a few minutes before eating. The cake is best consumed while still warm or within a few hours of it being cooked.
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.