Place milk in a large stockpot and stir in the salt. If you have a candy thermometer, clip it to the side of the pot to keep an eye on the temperature.
Set the milk on medium heat until it reaches 185F. Small curds should begin to form.
Stir in the lemon juice.
Reduce heat to medium-low, while maintaining the temperature of 185F for 20 minutes.
Remove milk from heat and let sit for a few minutes before straining.
Line a fine mesh sieve/strainer with cheesecloth and either pour the milk mixture into that, or transfer curds individually with a spoon. You can either discard the whey (liquid) or save a cup to store the ricotta curds in.
Notes
Whey Leftovers: Use the leftover whey to make lots of different things, from homemade yogurt to beauty products. Whey is great for making traditional ricotta as well.
Fresh Lemon Juice: You can use fresh lemon juice instead of lemon juice from a bottle.