Preheat the oven to 350°F. Toast the walnuts on a rimmed baking sheet in the oven for approximately 8 minutes. After they turn slightly golden, take them out of the oven to cool.
Chop the garlic in the food processor for several pulses.
Place the basil, nutritional yeast, lemon juice, sea salt, and walnuts in the bowl of the food processor. Pulse several times until mixed. Scrape down the sides as needed.
Add olive oil in a steady stream and continue pulsing until it is combined. Serve immediately. See notes for storage instructions.
Notes
For a thinner pesto, add water, a tablespoon at a time, until you achieve the desired consistency.
Place pesto in an airtight glass container and refrigerate for up to 5 days.
To freeze, place pesto in an ice cube tray. Once frozen, place the cubes in a Ziploc bag and store them in the freezer for up to 4 months.