Name: Onion Omelet
Ingredients: 1 large Spanish onion; ¼ teaspoon coarse sea salt; 2 ounces butter; 1 pint cold water; pepper to taste

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 ↓

Onion Omelet

Ingredients

Directions

Prepare

Peel and quarter the onion.
In a saucepan, combine the onion, salt, butter, and cold water.

Cook and serve

Simmer gently until the onion is tender, about 30 minutes.
Pour into a heated bowl, sprinkle with pepper, and serve hot.

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.

Onion + peppertop 11% of all pairs

Smell alikemoderate

Cooked together68,474 recipes

Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
Onion + buttertop 15% of all pairs

Smell alikemoderate

Cooked together42,912 recipes

Shared aroma: decanal (soap, orange peel).
Butter + peppertop 21% of all pairs

Smell alikemoderate

Cooked together85,593 recipes

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

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

What each ingredient does

Spanish onion: Forms the tender, mild body of the dish as it simmers slowly.
Butter: Adds fat and richness, carrying flavour through the gentle simmer.
Cold water: Provides the liquid that gently cooks the onion until tender.