Blend the spinach, basil, pine nuts, Parmesan cheese, salt, pepper, lemon juice, lemon zest, and 2 tablespoons of the oil in a food processor until nearly smooth, scraping the sides of the bowl with a spatula as necessary. Drizzle the remaining oil into the mixture while processing until smooth.
Divide pesto evenly in an ice cube tray. Wrap in plastic wrap and freeze. Once pesto is frozen, remove from tray and store in a heavy-duty freezer storage bag and use as needed.