Try this:
Place a thick slice of lemon on a paper towel and microwave it on high for 1 to 1 1/2 minutes. Let it stand overnight or until the liquid has cooled.
Or
Pour 1/2 c. bottled lemon juice into a microwave-safe bowl or a 2-c. glass measuring cup (if you don't have a fresh lemon) and follow the same directions. You can also dilute the lemon juice with water and add several whole cloves.
Wipe the microwave's insides with a paper towel soaked in a water-and-lemon-juice solution. Clean the top, bottom, sides, window, door, door seals and seams. Wipe dry.