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 ↓
Quickly-made Tomato Soup
Ingredients
Directions
Prepare
Peel and slice the onion.
Cut the bacon into pieces and fry it in a saucepan.
Make the soup
Add the onion to the bacon fat and fry until softened.
Sprinkle in the flour and gradually stir in a little water until it boils.
Pour in the remaining water and add the tomatoes (sliced if fresh).
Add salt and pepper, then simmer for about 20 minutes (1 hour if using fresh tomatoes).
Strain the soup through a colander 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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Onion + peppertop 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 flavour and body of the soup.
- Flour
- Thickens the liquid as it cooks, giving the soup body.
- Bacon fat
- Carries flavour and adds richness to the onion and base.
- Onion
- Adds savoury sweetness and aroma as it softens in the fat.
The step that matters
Adding the flour to the fat. Flour stirred into hot fat and then liquid must be blended gradually so it hydrates evenly; adding it all at once or skipping the stir forms lumps and leaves the soup unevenly thickened.
Flavor stand-ins for the onion
How well each one fits the dish's main ingredients (tomato, butter, flour, pepper):
- Capsicumbetter flavor fit
- Okrabetter flavor fit
- Eggplantbetter flavor fit
- Onionthe original
Fit is the average pairing score against tomato, butter, flour, pepper. 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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