Heat the milk in a large pot over medium heat to between 185° and 200°F. Add the lemon juice and stir it in slowly, using gentle up-and-down motions, for one minute.
Cover the milk and allow it to sit, undisturbed, for 15 minutes, or until you recognize a clean break. If you have not gotten a clean break after 20 minutes, add a bit more lemon juice and wait another 15 minutes, or until it does set.
Line a colander with butter muslin, and gently ladle the curds from the pot into the colander. Tie the corners of the butter muslin together to create a draining bag, and suspend it to drain for 1½-2 hours, or until it stops dripping.
Take the cheese out of the butter muslin and place it in a large, clean bowl. Mix in the salt.
Add additional ingredients such as herbs, spices or fruit, as desired.
Cover and refrigerate until ready to use. Keeps for up to 2 weeks.