Get rid of excess debris
You need to start by getting rid of excess debris and other waste materials inside your oven. You can do this with the help of a damp cloth. Keep in mind that the lemon will only help remove the grease and dirt. Crumbs and other large debris will serve as hindrances in the cleaning process, so pick these out beforehand.
Place lemon in microwave safe bowl
You need to place lemon slices in the microwave safe bowl, and then add around two to three cups of water to the bowl. If you do not have lemons available, you can use lemon juice; simply pour two to three tablespoons of lemon juice in the microwave safe bowl.
Place the bowl in the oven
Next, you need to place the microwave safe bowl containing lemon and water in the microwave. Then, you need to boil the solution for two to three minutes in the microwave. By doing this, you will create a lemon-infused steam which is helpful in removing the stains, and which will coat the interior of the oven.
Leave the bowl in for few minutes
After boiling the solution, you need to leave the microwave safe bowl in the microwave oven for five to seven minutes. By doing this, you will build up more steam inside the microwave oven, as the hot water will continue to let off steam inside.
Remove the bowl and wipe the microwave
Finally, you need to remove the bowl, and wipe down the insides of the microwave with help of a damp cloth or rag. By doing this, you will remove all the grease and stains on the inside of the microwave.