L.A.
Ugh, it is the worst smell.
Wipe out the microwave really well. Remember the inside of the door, and the top of the inside of the microwave. Dry it off really well.
In a microwave proof bowl you can either use, lemon juice (1 lemon) and 1 cup water. Microwave 2 min and leave in there for 5 minutes.
Or Vinegar (1/2 cup) and water (1 cup). Micro 2 min. let sit 5 min.
Or baking soda (1/4 cup) and water (1 cup).Micro 2 min. let sit 5 min.
Then wipe down the microwave again with a clean sponge. Place a dry newspaper in the microwave and let the microwave dry out. Should take the smell away.