Pour milk and cream into a heavy stockpot or Dutch oven. Add salt to the milk mixture.
Heat over medium heat, stirring frequently to prevent the milk from scorching on the bottom of the pan.
Heat until the temperature of the milk registers between 185°F and 195°F. At this temperature, the milk will be slightly foamy on the top, but not boiling.
Add lemon juice to the milk mixture and stir. You should see the milk curdling almost immediately. Turn off the heat when the mixture starts to separate and leave it to sit for about 10-15 minutes.
Line a strainer or sieve with several layers of cheesecloth for draining the ricotta.
Use a slotted spoon to lift the cheese curds from the whey and transfer to the cheesecloth-lined strainer. Allow the ricotta to drain for as long as you wish - the longer it drains, the thicker it will be. You can drain it for just a few minutes for a creamy ricotta or up to 45 minutes for a thicker ricotta.
Transfer ricotta to an airtight container and refrigerate or serve immediately.
Store in an airtight container in the refrigerator for 3-4 days.
