Heat the milk with the lemon juice in a stainless steel or other nonreactive pot over medium-low heat only until the curds separate from the whey; do not let the milk scorch.

Line a colander with three layers of cheesecloth. Pour the mixture into the colander. Bring the ends of the cheesecloth together and tie them securely with kitchen twine. Tie the twine to a wooden spoon handle. Rest the spoon with the cheesecloth over a deep bowl. Depending on the consistency you desire, allow the bag to hang for 2 to 3 hours in the refrigerator. The longer you leave it, the stiffer the curds will become.

When it is ready, unmold the cheese. Season with salt and store in an airtight container in the refrigerator for 3 days. You might also season the ricotta with minced chives or green garlic, cracked black pepper, and a little olive oil.