Toast pumpkin seeds in a 350 °F oven for 8-10 minutes, shaking the pan after 5 min.
Combine toasted pumpkin seeds, basil, garlic, and salt in a food processor and process while you add the olive oil in a slow, steady stream. Add the nutritional yeast and lemon juice, and pulse to combine. The sauce should be the consistency of a slightly grainy paste.
Use this sauce as a dip, spread on bread, tossed with pasta, on pizza or as a spread for sandwiches. Store leftovers in the fridge and use within a week.
Check your nutritional yeast and pumpkin seeds for potential cross contamination. Source a brand/packaging option that is safe for your needs.