In a large pot, gently heat the milk over medium heat until it reaches a temperature just below boiling, around 200°F. Stir occasionally to prevent scorching.

Remove the pot from heat and add the vinegar or lemon juice and salt, stirring gently to combine.

Allow the mixture to sit undisturbed for 10 to 15 minutes. The milk will separate into curds and whey during this time.

Line a colander with a few layers of cheesecloth and place it over a large bowl. Carefully pour the curdled milk into the colander, letting the whey collect in the bowl below.

Let the curds drain for 20 to 30 minutes, depending on your desired consistency. For wetter ricotta, drain for less time; for drier ricotta, allow it to drain longer.

Transfer the ricotta to a container and use immediately, or store in the refrigerator for up to 4 days.