Combine arugula, garlic, Parmesan cheese, pepitas, lemon juice and red pepper flakes (if using) in a blender or a small food processor.
2 cups tightly packed fresh arugula, 1 clove garlic, ½ cup shredded Parmesan cheese, ½ cup pepitas, 2 tablespoons freshly squeezed lemon juice, 1 pinch red pepper flakes
Pulse until combined and then, with the blender or food processor running, drizzle in olive oil until a pesto forms, scraping down sides as needed. (If your blender or food processor doesn't have a chute to add ingredients while it's running, add half the oil, blend it in, and then add the other half, and blend it in.)
½ cup extra virgin olive oil
Taste, and season with salt and pepper if needed.
Video
Notes
Parmesan cheese: For the best flavor and texture, I recommend shredding your own Parmesan cheese. Pre-shredded Parmesan tends to be a little hard. I don't advise using shelf-stable grated Parmesan for this recipe.
Refrigerate/Freeze: Arugula pesto can be refrigerated in an airtight container for up to 5 days. For best color, press a piece of plastic wrap directly onto the surface or drizzle a thin layer of olive oil on top before covering. It also freezes well. Portion the pesto into ice cube trays, freeze until solid, and transfer to a freezer bag for up to 3 months.
Variations: You can swap in cashews, pine nuts, almonds, or walnuts if you prefer them instead of pepitas. Lightly toasting the nuts will enhance their flavor. Adjust the amount of garlic to your liking, or omit it completely.