Collocations for onion - noun

raw
caramelized, pickled (esp. BrE)
a jar of pickled onions

chopped, diced, sliced
Put the chopped onion and garlic in the pan …

green (AmE), spring (BrE)
cocktail, pearl (esp. AmE), red, sweet (esp. AmE), Vidalia™ (AmE), etc.

chop, peel, slice
brown, soften
cook, fry, grill (esp. AmE), sauté
garnish sth with
Garnish with a little chopped onion.

grow

ring
soup
dip (esp. AmE)
skin
set (technical)
dome
the onion domes of St Basil's Cathedral

cheese and onion (BrE)
cheese and onion flavoured crisps

sage and onion (BrE)
sage and onion stuffing