Lemon juice is my acidic salt: it brightens a soup, balances the sweetness of pumpkin and carrots, and freshens a tahini sauce or a hummus. In vegan recipes it is also a small technical ally, because it helps soy milk mayonnaise thicken and gives almond ricotta the right tangy note.
Always squeeze it fresh and strain it through a sieve to remove seeds and pulp. On cut artichokes or apples it keeps them from browning.
When I can, I choose organic lemons: that way, after squeezing them, I can also use the grated zest and waste nothing.