Wash your carrot tops well, and set them aside to dry. Pulse the pepitas and the garlic in a food processor with pinches of salt and pepper. Add the carrot tops and pulse again. Add the lemon juice and pulse again, scraping down the sides of the food processor as needed. While the blade is running, drizzle in the olive oil until the pesto blends smoothly. Taste and adjust seasonings. Add parmesan cheese, if desired. Add additional olive oil (and/or 2 tablespoons water) for a thinner consistency, if desired.