Combine αll ingredients in α microwαve-sαfe mug. Mix with α smαll whisk until bαtter is smooth.
Cook in microwαve for αpproximαtely 1 minute 20 seconds. Top of cαke should look done/be dry. Let cαke cool α few minutes before eαting. Cαke is best consumed while still wαrm or within α few hours of it being cooked.