Why it works: Tomato and pepper are a kitchen classic. They rank in the top 7% of all ingredient pairs, and 17,923 recipes mention both. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓
Quick Tomato Soup
Ingredients
Directions
Mix the water, tomatoes, salt, and pepper in a pot.
Heat the mixture to boiling.
In a separate bowl, rub the butter and flour together to form a paste.
Add the butter‑flour paste to the boiling soup and cook for a few minutes.
Strain the soup and serve.
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.
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 + peppertop 7% of all pairsAroma overlapmoderateMentioned together17,923 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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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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Pepper + oniontop 11% of all pairsAroma overlapmoderateMentioned together68,474 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).
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Butter + oniontop 15% of all pairsAroma overlapmoderateMentioned together42,912 recipes
Shared aroma: decanal (soap, orange peel).
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
- Provide the main body, flavor, and acidity of the soup.
- Butter
- Adds richness and fat, carrying flavor and smoothing the texture.
- Flour
- Thickens the soup with the butter as a roux-style paste.
The step that matters
Adding the butter-flour paste to boiling soup. Flour thickens best when it is worked into fat first and then whisked into hot liquid. Adding it in lumps or to a soup that is not hot enough can leave clumps that do not smooth out, so the paste should be stirred in well and cooked for a few minutes to lose its raw flour taste.
Flavor stand-ins for the onion
How well each one fits the dish's main ingredients (tomato, pepper, butter, flour):
- Capsicumbetter flavor fit
- Okrabetter flavor fit
- Eggplantbetter flavor fit
- Onionthe original
Fit is the average pairing score against tomato, pepper, 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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