Why it works: Tomato and pepper are a kitchen classic. They rank in the top 7% of all ingredient pairs, and cooks put them together in 17,923 recipes. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓
Tomato Soup
Ingredients
Directions
Cook the soup
Boil tomatoes and herbs in soup stock.
Once cooked, mix flour with water to make a smooth paste.
Thicken the soup with the flour mixture.
Strain the soup, then season with butter, pepper, and salt.
Serve
Serve hot.
Transcribed from a scanned cookbook and modernised for today's kitchens. Where the book gave no heat or time, or said "a moderate oven", the temperatures and times here may be modern equivalents rather than the book's own figures.
Photo for illustrative purposes only · Contact us to use it
Explore the science
The flavor team
The pairs that carry this dish. Each one is judged two ways: how much their aromas overlap, and how often cooks already put them together.
-
Tomato + peppertop 7% of all pairsSmell alikemoderateCooked together17,923 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
-
Flour + buttertop 12% of all pairsSmell alikelowCooked together124,287 recipes
Shared aroma: isobutyraldehyde (malty, green).
-
Flour + peppertop 19% of all pairsSmell alikemoderateCooked together50,459 recipes
Shared aroma: isobutyraldehyde (malty, green).
-
Butter + peppertop 21% of all pairsSmell alikemoderateCooked together85,593 recipes
Shared aroma: trans-2-nonenal (cardboard, fatty).
-
Tomato + buttertop 22% of all pairsSmell alikemoderateCooked together6,918 recipes
Shared aroma: 3-hexenal (apple, fruity).
Flour and butter barely smell alike, yet cooks put them together in 124,287 recipes: they work on texture and structure more than aroma.
Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs
What each ingredient does
- Tomatoes
- Provide the main body, acidity and sweet flavour of the soup.
- Soup stock
- Forms the liquid base that carries the flavour of the tomatoes and herbs.
- Flour
- Thickens the soup as its starch swells and sets when heated in liquid.
- Butter
- Adds richness and a smooth, rounded mouthfeel at the end.
- Herbs
- Add aromatic flavour as they simmer in the stock.
The step that matters
Thickening with the flour mixture. Mixing the flour with water first into a smooth paste prevents lumps, because dry flour clumps when added straight to hot liquid. The starch then needs to be heated in the soup so it thickens fully.
Swap the tomato
How well each one fits the dish's main ingredients (flour, butter, pepper):
- Shallotfits better
- Chivefits better
- Capsicumfits better
- Tomatothe original
Fit is the average pairing score against flour, butter, pepper. Candidates are from the same food group and used in at least 100 recipes.
“What each ingredient does” and “The step that matters” were written by Claude from this recipe’s own method and reviewed in samples by CompKitchen.
More tomato soup recipes
You might also like
The free Flavor Lab newsletter: one surprising pairing a week and the molecular reason it works, in 60 seconds. No spam, unsubscribe anytime.
Prefer an account? Create a free account to save pairings and unlock the full chemistry.

Tomato Bisque61 recipes
Tomato Fritters23 recipes
Tomato Puree23 recipes
Macaroni with Tomato Sauce16 recipes