Using a large microwavable bowl (I prefer my 1 quart Pyrex glass measuring cup), place 3-4 cups of hot water and at least 1 cup of lemon juice (I buy in bulk, so I have tons to spare) in the microwave for 5-6 minutes (a little longer for those really dirty appliances, like moi). After it does it's biznas, allow the container to sit in the microwave for at least a minute. Remove (CAREFULLY AS IT WILL BE PIPPING HOT) and immediately use a damp sponge or paper towel to wipe out the microwave. The
Yay to that!
Plus, it leaves your microwave smelling of fresh lemon-ey goodness! I prefer to keep the door open for a bit to let the smell waft through my kitchen and I also leave the used lemon-water out for fragrance purposes too! I also like to pour the leftovers into the toilet as it does freshen the potty room a bit too. That might be a little odd, but who cares!??
Go forth and clean thy kitchen!