1. Place inside a 4-cup large microwave-safe bowl that contains 1 cup of water and a chopped-up lemon, lime, or orange or several tablespoons of vinegar. 

2. Turn on High for several minutes or until the solution boils and the window is steamy.

3. Let it sit to cool for 15 minutes before opening the door. Remove and wipe out inside.

4. Clean the rubber gasket around the door with a sponge dampened with water only. If the window is greasy, clean with a mixture of half vinegar and half water, then dry.