In a food processor (or blender on low speed), add the basil leaves, baby spinach (or other greens), tomato, garlic and lemon juice. Process until just blended and reduced in volume.
Add the pepitas and and process until blended but still chunky, stopping to scrape down the sides as needed. (See notes.)
Season with sea salt freshly ground black pepper to taste.
If your tomato has a lot of liquid, you may want to drain away some of it or add a little tomato at a time so the sauce isn't too watery. Also, you can add more pepitas or a tablespoon or two of nutritional yeast if needed, to thicken.
Pepitas don't have shells and are only found in certain types of pumpkins. Don't substitute pumpkins seeds in their shells for this recipe! Raw seeds work well here, but I've also used tamari roasted seeds, which are delicious!
I've made this recipe in both the food processor and the blender. I like this sauce chunky, and the food processor is a better option for that. It takes a little longer, up to a minute or so. If you use the blender, process on low to keep the sauce chunky, if desired.
You can store this pesto in the refrigerator for up to a week, or in the freezer for about 3 months.