In a food processor or high-powered blender add walnuts, garlic, basil, parmesan, lemon zest and salt.
Begin processing as you drizzle in the olive oil. Pesto should slowly come together to form a textured paste.
Serve stirred through pasta, dolloped on to crunchy roast potatoes or smeared on grilled chicken with mozzarella and tomatoes. To store, decant into an airtight jar. Can be kept in the refrigerator for up to five days.