Tomatoes are probably the hardest nightshade to replace for two reasons: 1.) tomato products come in so many shapes and forms that they are useful in all kinds of recipes, and 2.) they are often a substantial part of the dish they inhabit. Think about it: tomato sauce, tomato salsa, minestrone soup. Tomatoes are not just ingredients in these recipes, they are the base of these recipes. But all is not lost! When you encounter a recipe with tomato in the ingredients list, ask yourself: what is the role of the tomato in this dish? Is it acting as the dish's acid? sweetener? thickener? is it, in the case of a salad, there for texture and color more than for flavor?
Before I start discussing replacing tomatoes, I want to introduce you to your two new best friends:
On the right, Tamarind Concentrate. I like the Laxmi brand, but you can find this in any Indian/Southeast Asian or Latin American grocery stores, or in a well-stocked grocery store's "ethnic food" section. Tamarind concentrate may also seem a little expensive, but a little goes a long way, and though you should keep it in the fridge once you open it, this too will last forever. (I have used tamarind that has sat in a fridge for about a year. The sugar in it crystalizes around the edge a little, but it was fine to eat.) It resembles molasses in appearance, but is much much tarter. It has a little sweetness to it, but is mostly sour. Any time a recipe calls for tomato paste, I use at least half tamarind paste to make up for it, because it resembles tomato paste in terms of taste in a recipe.
If you want to substitute effectively, those are essentials. Below I will list how to substitute for (most) tomato products.
Replacing Raw and/or lightly-cooked Tomatoes
For the most part, raw tomatoes are often present in recipes to help add a bit of tartness, crispness, and color. To achieve similar flavor, you can use an under-ripe mango. I know this sounds crazy, but hear me out: an underripe mango has not ripened enough to be sweet, and it has a tartness and near-sweetness reminiscent of a tomato. Sliced, the fruit's texture is also similar to a thick slice of tomato. You want a mango that has only the tiniest bit of give when you squeeze it with your fingers--it shouldn't feel soft by any means, but it shouldn't be as hard as rock. Peel it, and either slice or cube it. This is perfect for sandwiches, salsas, and cold salads. You can also ad it last-minute to stir fries, but if you cook it too long, it will become sweeter. In a cold salad (grain, pasta or vegetable), you can also substitute raw zucchini or summer squash for raw tomato. Diced it small and add a small amount (about 1 tsp per tomato replaced by zucchini) of lemon juice to the recipe. Also consider substituting or adding cucumber, which provides the same watery, crisp texture as raw tomato.
For lightly-cooked tomatoes, like the kind you might have in an English breakfast or on Eggs [Tofu] Benedict or Florentine, lightly sautee sliced or fileted zucchini in a small amount of olive oil and vinegar over high heat until it begins to soften and brown on each side.
Replacing Tomatoes in Cooking
I have some bad news for you: if a recipe calls for an entire can or more of diced, crushed, stewed, peeled, ground, or pureed tomatoes, I can't help you. One can or more of tomatoes means that they are a significant part of the recipe that you are better off looking for a different recipe. But don't give up hope; lots of dishes that call for those ingredients are also available nightshade-free. For example, though minestrone soup usually calls for diced tomatoes, I have seen recipes without any. (Search engines' "advanced search" option lets you find recipes that don't include a word [like tomato].) You can find variations on curries that call for cans of tomatoes that instead call for a little tomato paste or a single chopped tomato (both of which are easier to substitute). Be creative, and don't despair.
First and foremost, if you're anything like me, you probably miss the occasional thick pasta sauce. I have a recipe for tomato-free marinara here, and you can find many others by a simple internet search. It may seem like a lot of work, but this stuff freezes well, and will help you out if you're missing this basic comfort food. You can also buy Nomato's nightshade-free marinara, barbeque sauce, or ketchup.
Mostly, though, in cooking, you'll need to replace a couple chopped tomatoes, or 1/4 C tomato paste, or a couple tablespoons of ketchup. Remember that tomatoes are primarily in these recipes to add some tartness, a hint of sweetness, and thickening properties. This is easy! And you have a variety of options. If the chopped tomatoes are supposed to remain whole throughout the recipe and not create a sauce, like in a sauteed pasta dish, you can substitute and equal amount of zucchini for the tomato. If the chopped tomato is supposed to cook down into a paste, treat it like tomato paste in a recipe, which you can substitute with:
- Canned pumpkin puree, butternut squash puree, or sweet potato puree. Obviously not the kind with spices in it. These thicken a recipe, and with a tiny addition of vinegar (or ume plum paste!) also provide the sweetness and acidity of a tomato.
- Umeboshi paste. I described this above, but this is great for adding to a tomato-textured thing, with tamarind to create the perfect fake-tomato paste taste, or by itself if you're just trying to replace the taste of tomatoes (like in salsa and other sauces, or curries).
- Tamarind Concentrate. Again, I discussed this above, but it's great for adding the zing you miss with tomatoes to a variety of recipes. It is especially good in seitan, or other recipes in which tomato paste serves as a moistener and flavor enhancer. Works especially well with umeboshi paste. Tamarind and a little sweetener of some sort is the best substitute for ketchup in recipes.
- Molasses. Molasses have such a strong, distinctive flavor that you only want to use a tiny bit of them, unless it's for something like BBQ sauce, which benefits from the taste of molasses. Combine this with one or more of the other options in recipes where tomato paste is added as a moistener and flavor enhancer.
- Peanut butter. I know how crazy this sounds, but in certain recipes, especially in seitan or meatloaf-imitations, peanut butter adds a nice texture and interesting depth of flavor. Plus, it acts as a thickener.
In the case of sundried tomatoes, I know, I miss them too (especially the oil packed ones! yum). Consider using olives in their place.
And with pizzas, while non-tomato marinara can do the trick, if you're anything like me, you'll come to a new appreciation of white pizza. And of pesto as pizza sauce.
Tomato dishes are so ubiquitous that few of us can imagine comfort food without them. But like I said above, be creative, and don't despair! Nightshade-free doesn't mean comfort-free. You have options.
One final note on avoiding tomatoes. As with peppers and potatoes, tomatoes can sneak into unexpected foods. Many fake meat products, especially veggie hot dogs, bacon, deli-style slices, and Italian-flavored sausages, use tomato paste for color and/or texture, so as always for the nightshade-free vegan, read ingredient labels carefully before buying fake meats. Sweet-and-sour sauce, many other flavorful Asian stir-fry sauces, and barbeque sauce almost always contain ketchup or tomato paste, as do most homemade seitan recipes, so check ingredient labels and be sure to ask about these things if you're at a restaurant or friend's house.