Place the milk in a large saucepan over a low-medium heat. Allow the milk to come to a simmer – about 10-15 minutes.
Once the milk is gently bubbling, turn the heat off and remove from the heat and the stove. Add the lemon juice and salt. Stir gently, only just to distribute the acid in the milk. Allow to sit for 15 minutes – the mixture should have curdled and become obvious ‘curds and whey.’ There should be ricotta like lumps of milk and an semi-transparent lemon coloured liquid
If the liquid is still milky and completely opaque, return the ricotta to a gentle heat until it begins to separate, and then take it off the heat again. You can add a little extra acid (a teaspoon at a time) as an insurance policy, although this might affect the taste of the final product.
Once you have left the mixture to sit for 15 minutes, the mixture should have obviously separated into the two distinct elements. Gently pour the ricotta through a sieve lined with muslin cloth or a nut milk bag. You can discard the whey or use it in smoothies or baking – see notes for a few more ideas.
How long you strain the ricotta is up to you – it depends on how runny you like your ricotta. I like mine on the more spreadable side, so I either give mine a good old squeeze and decant, or strain mine for a maximum of around 20 minutes. Anywhere from 20 minutes to 1 hour is a good ballpark. If you accidentally overstrain, you can add a little milk to loosen it up.
Check for seasoning and add in the lemon zest and pepper. Allow to cool, and if you're not using immediately, store in an airtight container in the fridge.