Unplug the microwave
Remove the turntable and wash it with warm soapy water
Wipe the interior with a mixture of equal parts water and white vinegar
Heat a bowl of water with lemon slices for 3 to 5 minutes
Leave the microwave door closed for 5 to 10 minutes after heating
Wipe the inside with a clean damp cloth
Sprinkle baking soda inside and leave it overnight
Place an open bowl of baking soda inside for several hours
Clean the door, seal, and vents
Repeat if the smell remains