I take a small glass microwave safe bowl and fill it with half a cup of water and two tablespoons of lemon juice. I heat it up for three minutes in my microwave and then let the water-lemon mixture sit for another 8-10 minutes.
I take the bowl out very carefully as that half cup of water is still quite hot. Taking a damp dish cloth or sponge I wipe the entire surface and the inside of the door of my microwave. I may have to do this several times rinsing out my sponge or dish cloth in the sink, until I get all residue.
How to Clean your Microwave https://www.inspiredhousewife.com/how-to-clean-your-microwave/