Tomato soup is a popular traditional soup that many people in the US associate with childhood. Tomato soup is often listed among popular comfort foods when paired with grilled cheese sandwiches. As a relatively blank slate, tomato soup can be tweaked to suit many different taste preferences with the careful use of spice. Here are some of the best tomato soup spices:
Onion
A versatile member of the Allium family, onions are viewed by most cooks as being essential for savory soups, including tomato soup. There are many different kinds of onions, including red onions, yellow onions, and scallions. Most of them will work well in tomato soup. You can use onion in the base of the soup itself and as a topping that you sprinkle on just before you serve it.
Onion can add a herbaceous umami quality that it is difficult to replicate with any other herb. Onions can also impart a nutty sweetness depending on the type of onion and how you use it.
Garlic
A close relative of the onion, garlic offers a nutty and richly aromatic flavor profile that many consider essential to savory dishes and especially those that rely heavily on tomatoes. Garlic is essential for marinara sauces and similar preparations, and it is just as valuable in a traditional tomato soup.
Of course, the traditional tomato soup will not be as heavily seasoned as pasta sauce, so you will want to use garlic carefully unless you want a particularly garlicky soup. It can easily overwhelm all the other flavors in the dish.
Bay leaves
The bay leaf comes from the bay laurel tree and has a distinctively savory flavor profile that makes it unique among most herbs used in European and American cooking.
Along with its powerful camphoraceous qualities, bay leaves have a mild bitterness that helps it to bring out the umami qualities in dishes. Bay leaves can be strongly flavored and should be used carefully.
Thyme
A member of the mint family, thyme gives tomato soup woodsy and mildly camphoraceous notes against a strong minty background. Thyme is a lot more on the savory side than mint even though it does share some aspects of its flavor.
Like other herbs in the mint family, thyme does go well with tomatoes. It works in dried or fresh form. Whether you use dried or fresh thyme, use it carefully. It is a strongly flavored herb that can completely dominate the flavor profile of your soup.
Basil
Another mint relative, basil is sweeter than thyme but not as sweet as mint. While it is not a classic tomato soup seasoning, the fact that pairs so well with tomatoes means that it can be used to place an enjoyable Mediterranean twist on a dish that is often not all that flavorful. Basil will give your soup licorice and mint notes with a hint of lemony citrus.
You can use dried or fresh basil, but the former should be added to the soup as it cooks, and the latter should only be added at the end of cooking time.
Parmesan
Tomato soup is often served along with grilled cheese sandwiches because the cheese flavor is considered complementary to the acidic fruitiness from tomatoes.
Adding Parmesan gives a cheesy flavor to the soup itself. Along with the taste of cheese, Parmesan is rich in glutamates. Glutamates provide the umami flavor and can help to make your tomato soup more savory.