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Sauce

Spanish or Portugal Onion Sauce

A savory onion sauce with gravy, red port, and butter, served as a condiment.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 8 ingredients
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Why it works: Pepper and lemon match in chemistry and in kitchens. They rank in the top 3% of all ingredient pairs, and 27,047 recipes mention both. Both carry trans-2-nonenal, which smells cardboard, fatty. The science ↓

Spanish or Portugal Onion Sauce

Ingredients

Directions

Prepare

  1. Roast the onions until they are slightly more than half done.

  2. Peel the onions and add them to the thickened gravy or coulis.

Make the sauce

  1. Season with salt and cayenne pepper.

  2. Add red Port, powdered sugar, and lemon juice.

  3. Boil until the onions are tender, then mash with butter.

  4. Serve as a sauce for your chosen dish.

Recipe from a historical cookbook (Internet Archive).

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.

  1. Pepper + lemontop 3% of all pairs
    Aroma overlapstrong
    Mentioned together27,047 recipes

    Shared aroma: trans-2-nonenal (cardboard, fatty).

  2. Onion + peppertop 11% of all pairs
    Aroma overlapmoderate
    Mentioned together68,474 recipes

    Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).

  3. Onion + buttertop 15% of all pairs
    Aroma overlapmoderate
    Mentioned together42,912 recipes

    Shared aroma: decanal (soap, orange peel).

  4. Lemon + buttertop 16% of all pairs
    Aroma overlapmoderate
    Mentioned together41,227 recipes

    Shared aroma: 3-hexenal (apple, fruity).

  5. Sugar + buttertop 17% of all pairs
    Aroma overlapmoderate
    Mentioned together98,233 recipes

    Shared aroma: guaiacol (smoky, sweet).

Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs

What each ingredient does

Mild onions
Provide the main body and sweetness that the sauce is built around.
Thickened gravy or coulis
Forms the liquid base and gives the sauce its body as the onions soften.
Red port
Adds sweetness and wine acidity that deepen the flavour as it simmers.
Butter
Adds fat for a smoother, richer mouthfeel when mashed into the sauce.

The step that matters

Boil until the onions are tender, then mash with butter. If the onions are not fully tender, the sauce stays grainy and raw-tasting. Boiling reduces the liquid and softens the onion cells, so mashing gives a smooth texture. Adding butter after mashing, off the heat, helps it emulsify into a glossy sauce.

Flavor stand-ins for the lemon

How well each one fits the dish's main ingredients (onion, pepper, sugar, butter):

  1. Lemonthe original
  2. Mangoabout as good a flavor fit

Fit is the average pairing score against onion, pepper, sugar, butter. 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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