Why it works: Tomato and onion are a kitchen classic. They rank in the top 8% of all ingredient pairs, and 20,633 recipes mention both. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓
Tomato Soup
Ingredients
Directions
Make the soup
Mix the first six ingredients.
Cook for ten minutes.
Rub through a sieve.
Add salt and baking soda.
Thicken and finish
Cook butter and flour together.
Thicken the soup with the butter and flour mixture.
Cook for two minutes.
Strain.
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 aroma chemistry they share, and how many recipes mention both.
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Tomato + oniontop 8% of all pairsAroma overlapmoderateMentioned together20,633 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Butter + flourtop 12% of all pairsAroma overlaplowMentioned together124,287 recipes
Shared aroma: isobutyraldehyde (malty, green).
-
Sugar + flourtop 15% of all pairsAroma overlapmoderateMentioned together92,116 recipes
Shared aroma: phenylacetaldehyde (hawthorne, honey).
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Onion + buttertop 15% of all pairsAroma overlapmoderateMentioned together42,912 recipes
Shared aroma: decanal (soap, orange peel).
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Sugar + buttertop 17% of all pairsAroma overlapmoderateMentioned together98,233 recipes
Shared aroma: guaiacol (smoky, sweet).
Butter and flour share little aroma chemistry, yet 124,287 recipes mention both: they likely 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
- Form the body and main flavour of the soup.
- Sugar
- Balances the tomatoes' acidity with sweetness.
- Onion
- Adds aroma and savoury depth to the soup.
- Baking soda
- Neutralises some of the tomatoes' acidity and deepens their colour.
- Butter
- Adds fat for richness and a smooth mouthfeel.
- Flour
- Thickens the soup as its starch swells when heated.
The step that matters
Cook butter and flour together. Cooking the butter and flour before adding them to the soup cooks the raw starch, removing a floury taste, and helps the flour blend in without forming lumps.
Flavor stand-ins for the onion
How well each one fits the dish's main ingredients (tomato, sugar, butter, flour):
- Capsicumbetter flavor fit
- Okrabetter flavor fit
- Sweet potatobetter flavor fit
- Onionthe original
Fit is the average pairing score against tomato, sugar, butter, flour. Candidates are from the same food group and used in at least 100 recipes. This compares flavor only: it does not check the job the ingredient does in the dish (bulk, moisture, acidity, structure).
“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.
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