Place one lemon on a cutting board or dinner plate, and slice the lemon in half with a knife. Leave the rind on the lemon.
Fill a microwave-safe bowl with 4 cups of water and one-half of the lemon. Hold the second lemon half over the bowl's water, and squeeze the lemon to place as much lemon juice in the water as possible. Place the squeezed lemon rind in the water.
Put the bowl inside the microwave oven. Close the oven's door, and set the oven to run for five minutes on high heat. Start the oven, and wait until it stops running.
Remove the bowl from the microwave oven using a potholder or oven mitt. Also remove the round carousel from inside the oven.
Dampen a kitchen sponge with water, and squeeze it to remove excess water. Use the sponge to wipe the interior surface of the microwave oven, starting with its ceiling and sides and working your way down to its floor. Rinse the sponge with water as needed, and continue wiping the oven's interior until it is clean.
Wash the carousel using 1 teaspoon of dish soap and the sponge, and then dry it well with a dish towel.