Instead of nuts, use seeds! I found that hemp and pumpkin seeds create the perfect texture.
Instead of using Parmesan cheese, use nutritional yeast for the cheesy flavor! However, I will admit, this may be an allergen for some (but it is rare).
Also, there are some that can’t handle citrus (also rare) but you can use apple cider vinegar instead of lemon juice or completely leave it out. If you choose to leave it out, make sure to eat it right away. The acid acts as a preservative to keep the pesto from browning.