1. With a vegetable peeler or a citrus zester, remove the zest from the lemons in thin strips. (Take care to avoid the bitter white pith). In a mortar or medium stainless steel or wooden bowl, combine the lemon peel and the salt. Pound and crush the peel with a pestle for several minutes to extract the oils. Use a circular motion to crush the peel against the bottom of the bowl as you dribble in the olive oil a little at a time and continue working the peel this way for about a minute.
2. Set the oil aside to infuse at least 1 hour and up to 6 hours, tasting it occasionally to gauge its strength, until it is pleasantly fragrant with lemon, but not cloying (If you let it steep too long, it will begin to taste like candy). Add additional olive oil if necessary to balance the flavor. Strain into clean, dry bottles and stopper.
Storage: This oil will keep several months refrigerated.
"Globally, 95 percent of our calories now come from 30 species," says journalist and educator Simran Sethi, author of Bread, Wine, Chocolate. "Three-fourths of the food we eat comes from 12 plants and five animal species."