Some people have an allergy or intolerance to nightshades including tomatoes, eggplant, potatoes, and bell peppers. If you need to avoid nightshades, try some of these substitutions: Instead of tomato sauce, you can make a pureed sauce with onions and carrots or winter squash. Pesto and sauces made with herbs, olive oil, or olives are also great choices. Or you can make a creamy Alfredo-style sauce using raw cashews or cauliflower. Instead of eggplant, substitute mushrooms such as cremini, portobello, or shiitake. Instead of potatoes, substitute cauliflower, sweet potatoes, winter squash, parsnips, or turnips. And instead of bell peppers, substitute celery or radishes.