Name: French Dressing
Ingredients: 1 large slice of onion; ½ teaspoon salt; ⅛ teaspoon pepper; 2 tablespoons vinegar; 4 tablespoons olive oil; ½ teaspoon Worcestershire sauce; 3 to 4 tablespoons tomato ketchup

Why it works: Sauce and ketchup match in chemistry and in kitchens. They rank in the top 1% of all ingredient pairs, and cooks put them together in 1,099 recipes. Both carry ethanol, which smells alcoholic, ethereal. The science ↓

French Dressing

Oven, in the book's wordsA hot oven

Ingredients

Directions

In a bowl, combine the onion, salt, pepper, vinegar, olive oil, Worcestershire sauce, and tomato ketchup, then mix thoroughly.
You can remove the onion or leave it in, based on your preference.

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 their aromas overlap, and how often cooks already put them together.

Sauce + ketchuptop 1% of all pairs

Smell alikestrong

Cooked together1,099 recipes

Shared aroma: ethanol (alcoholic, ethereal).
Olive + tomatotop 1% of all pairs

Smell alikemoderate

Cooked together15,539 recipes

Shared aroma: 3-hexenal (apple, fruity).
Pepper + tomatotop 7% of all pairs

Smell alikemoderate

Cooked together17,923 recipes

Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
Onion + tomatotop 8% of all pairs

Smell alikemoderate

Cooked together20,633 recipes

Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
Onion + olivetop 8% of all pairs

Smell alikemoderate

Cooked together29,779 recipes

Shared aroma: 2,4-decadienal (seaweed).

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

What each ingredient does

Olive oil: Provides fat that carries flavour and gives the dressing a smooth, pourable body.
Vinegar: Adds acidity that brightens the dressing and balances the richness of the oil.
Tomato ketchup: Contributes sweetness, tomato flavour and thickness to the dressing.

Swap the onion

How well each one fits the dish's main ingredients (pepper, vinegar, olive, sauce, tomato, ketchup):

Capsicumfits better
Mustardfits better
Cucumberfits better
Onionthe original

Fit is the average pairing score against pepper, vinegar, olive, sauce, tomato, ketchup. 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.