Natural form

A single yellow onion showing its papery amber-golden skin and rounded bulb form.

Shows the exterior identification markers — dry papery skin, amber-gold color, and bulb shape — that distinguish yellow onions from white or red varieties.

Produce

Yellow Onion

The aromatic backbone of soups, sofritos, and braises

Sharp and pungent raw, sweet and golden once caramelized, the yellow onion starts more dishes than any other vegetable. Keep it somewhere dark and dry and it'll last a month.

The yellow onion is the quiet engine of the kitchen — sharp and eye-watering raw, but slowly coaxed in fat it turns sweet, golden, and deeply savory. A balance of sulfur compounds (the bite) and sugars (the sweetness) makes it the default base for stocks, soups, sofrito (a slow-cooked aromatic base), mirepoix (the onion-carrot-celery base), and braises across nearly every cuisine. Few dishes start without it.

Measured in: piece
Storage: Dark Cool
Shelf life: 30 days

Find it in

Produce

Types & varieties

Spanish onion

Larger, milder, juicier — good for rings and gentle cooking

White onion

Sharper, cleaner bite; common in Mexican cooking

Red onion

Milder and pretty raw; bleeds color when cooked

Sweet onion (Vidalia, Walla Walla)

Low sulfur, high sugar; best raw or lightly cooked

How to choose

Pick onions that feel heavy and rock-hard with tight, dry, papery skin and a small neck. Avoid any that give under pressure, show green sprouts at the top, or smell musty — those are breaking down inside.

Heavy for its size = dense and fresh
Dry, crackly skin
No soft neck or sprouting

How to store

Keep whole onions in a cool, dark, dry, airy spot — a basket or mesh bag in the pantry, never sealed in plastic. Don't store them next to potatoes; the moisture and gases they swap speed spoilage in both. Cut onions go in a sealed container in the fridge for a few days.

How to prep (and stop crying)

Trim the top, halve through the root, peel, then slice or dice with the root left intact to hold the layers together. The root holds the most sulfur compounds, so cutting it last means fewer tears. A sharp knife bruises fewer cells (less released irritant), and chilling the onion 15 minutes first helps too.

Common uses

French onion soupSofrito and mirepoix basesCaramelized onions for burgers and tartsOnion gravyCurries and dalsPickled onionsStews and braisesRoasted alongside meats

Tips & pitfalls

Sweat onions low and slow for a sweet, translucent base; brown them harder for depth in soups and ragùs
True caramelized onions take 40+ minutes on medium-low — anything faster is just browned
A pinch of salt early draws out moisture and speeds softening
Soak raw onion slices in cold water 10 minutes to tame harshness for salads and sandwiches
Save peels and trimmings in the freezer for stock

Nutrition

40kcal

Energy

167 kJ · per 100 g

Where the calories come from

Protein 10%Carbs 88%Fat 2%

Protein

1.1g

2% DV

Carbs

9.3g

3% DV

Fat

0.1g

0% DV

Fiber

1.7g

6% DV

Sugars

4.2g

of which

Sodium

4mg

0% DV

Notable micronutrients

Vitamin C8% DV

Vitamin B67% DV

Folate5% DV

Thiamin (B1)4% DV

Potassium3% DV

Riboflavin (B2)2% DV

Source · USDA FoodData Central · Onions, raw

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In the shops

Matched grocery products

Onions
1 kg · Mercadona
€2.40
Sweet Onions
1 kg · Mercadona
€2.50
Onions
2 kg · Mercadona
€3.90
Red Onions
1 kg · Mercadona
€2.00
Diced Onion
BONPREU · kg · Bonpreu
€1.00
Red Onion 1 unit
ud · Bonpreu
€0.68

Good to know

Peak season: Storage onions year-round; harvested late summer/fall
Flavor: Pungent and sharp raw; sweet, mellow, savory when cooked
Origin: Central Asia; cultivated for over 5,000 years
Nutrition: ~40 kcal/100g; vitamin C, fiber, quercetin
How to buy: Firm, heavy, dry papery skin; no soft spots, sprouts, or musty smell

Substitutes