Why it works: Onion and pepper are a kitchen classic. They rank in the top 11% of all ingredient pairs, and cooks put them together in 68,474 recipes. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓
Tomato Sauce
Ingredients
Directions
Fry the onion in the butter until light brown.
Add the flour and cook together.
Add the stewed tomatoes and stir until thickened.
Season with pepper and salt.
Nutrition, whole recipe (rough)
What these numbers assume: 5 portions
| Ingredient | Portion assumed | kcal |
|---|---|---|
| Flour | 1 cup (125g) all-purpose | 455 |
| Butter | 1 tbsp (14g) | 102 |
| Onion | 1 medium (110g) | 44 |
| Black Pepper | 1 tsp ground (2.3g) | 6 |
| Salt | 1 tsp (6g) | 0 |
One typical portion per ingredient; the recipe's quantities are not counted. A rough guide only, not for medical or dietary planning.
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. See the original page.
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.
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Onion + peppertop 11% of all pairsSmell alikemoderateCooked together68,474 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
-
Butter + flourtop 12% of all pairsSmell alikelowCooked together124,287 recipes
Shared aroma: isobutyraldehyde (malty, green).
-
Butter + oniontop 15% of all pairsSmell alikemoderateCooked together42,912 recipes
Shared aroma: decanal (soap, orange peel).
-
Flour + oniontop 17% of all pairsSmell alikemoderateCooked together32,460 recipes
Shared aroma: isobutyraldehyde (malty, green).
-
Flour + peppertop 19% of all pairsSmell alikemoderateCooked together50,459 recipes
Shared aroma: isobutyraldehyde (malty, green).
Butter and flour 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
- Butter
- Carries the onion's flavor and adds richness while it browns slightly.
- Flour
- Thickens the sauce as its starch swells in the hot liquid.
- Stewed tomatoes
- Supply the main liquid, body, and tomato acidity to the sauce.
- Minced onion
- Adds aroma and savory sweetness as it softens and browns in butter.
The step that matters
Add the stewed tomatoes and stir until thickened. Stirring keeps the flour and butter mixture smooth as the liquid goes in, which prevents lumps. The starch must heat fully to swell and thicken the sauce properly.
Swap the onion
How well each one fits the dish's main ingredients (butter, flour, pepper):
- Shallotfits better
- Chivefits better
- Capsicumfits better
- Onionthe original
Fit is the average pairing score against butter, flour, 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.
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