Why it works: Pepper and lemon match in chemistry and in kitchens. They rank in the top 3% of all ingredient pairs, and cooks put them together in 27,047 recipes. Both carry trans-2-nonenal, which smells cardboard, fatty. The science ↓
Onion Sauce
Ingredients
Directions
Prepare the onions
Peel the onions and place them in a saucepan with cold water, then bring to a boil, drain and refill with boiling water.
Repeat this process 2–3 times to mellow the onions.
For Spanish onions, boil them once in milk.
Make the sauce
Chop the onions into flakes, then melt the butter and mix it with the chopped onions.
Alternatively, beat the onions to a pulp and strain through a sieve for a cream-like sauce.
For a brown onion sauce, slice the onions and sauté them in butter until light brown.
Dust with flour.
Add the beef gravy and cayenne pepper, then simmer until thickened.
Strain if desired, and add lemon juice before serving.
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 their aromas overlap, and how often cooks already put them together.
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Pepper + lemontop 3% of all pairsSmell alikestrongCooked together27,047 recipes
Shared aroma: trans-2-nonenal (cardboard, fatty).
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Onion + beeftop 7% of all pairsSmell alikemoderateCooked together17,092 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Butter + milktop 7% of all pairsSmell alikemoderateCooked together81,283 recipes
Shared aroma: (z)-4-heptenal (biscuit, cream).
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Beef + peppertop 10% of all pairsSmell alikemoderateCooked together18,971 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Onion + peppertop 11% of all pairsSmell alikemoderateCooked together68,474 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs
What each ingredient does
- Onions
- Provide the main flavour and body of the sauce as they soften and break down.
- Butter
- Adds richness and carries flavour, and browns the onions when sautéed for a brown sauce.
- Flour
- Thickens the sauce as it cooks with the butter and liquid.
- Beef gravy
- Supplies the savoury liquid base that the sauce simmers in.
- Lemon juice
- Adds acidity that brightens the rich onion and gravy flavours.
The step that matters
Dusting with flour before adding the gravy. Flour must be cooked briefly in the butter and onions so it thickens smoothly; adding liquid without this step can leave lumps and a raw starchy taste.
Swap the onion
How well each one fits the dish's main ingredients (butter, milk, beef, pepper, flour, lemon):
- Potatofits better
- Asparagusfits better
- Capsicumfits better
- Onionthe original
Fit is the average pairing score against butter, milk, beef, pepper, flour, lemon. 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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