Microwave milk for 30 seconds or until just slightly warm.
Mix in lemon juice (or vinegar) and stir a few times until lemon juice has reached all parts of the milk.
Microwave the mixture for 40 seconds. You should see small pieces of a soft white substance (your cheese) floating in a clear yellowish liquid (whey).
Put the mixture over a strainer and drain out the whey by pressing with a spoon. Flip the cheese upside down and strain again. Press a clean napkin against the strainer under the cheese towards the end of the straining process.
Move the cheese to a bowl and enjoy.
If not used immediately, spread cheese on a cheesecloth or a clean tablecloth and let sit over a bowl or cup for at least one hour to drain away more of the whey. Squeeze cloth to get rid of the last bit of liquid.
Run cheese in a food processor if you wish for a smoother texture. Use within a week.