Mix milk, lemon juice, and salt in a saucepan. Heat on medium heat until it reaches 190° using a candy thermometer.
Once it hits 190° remove it from the heat and let sit for 10-20 min until you start to see the curds separate from the whey.
Pour mix into a colander inside a bowl, lined with cheese cloth and pull the sides together to form a bag. Use kitchen string to tie the sides together and hang from a cabinet knob to let all the whey separate from the curds.
After about 5-7 hours and no more whey is dripping off the bag, take it down and open it up. You should have straight ricotta cheese in the bag! Store in a container in the fridge for up to 2 weeks, or use right away!