In recipes it's rare that you use an entire lemon - both the zest and the juice or even the whole lemon. Save these lemon leftovers (squeezed or hard, dried lemons work too) to clean the microwave with. I place any leftover lemon pieces in a microwaveable bowl filled halfway with water and microwave for 1-2 minutes until the microwave is filled with condensation. Then I wipe it down with a paper towel and all the grease and things that go "pop" in the microwave come right off. I never have to scrub the microwave anymore.
Make the microwaved lemon solution do double duty by dumping it down the disposal with some ice cubes to freshen up your sink.