fresh

slice, wedge
Garnish the fish with wedges of lemon.

cake, tart, etc.

squeeze
Squeeze a quarter of a lemon over the fish.

slice
garnish sth with

tree
pip (BrE), seed (esp. AmE)
peel, rind, zest
juice
slice, wedge

Lemon is used with these nouns:
cake, flavour, icing, jelly, juice, pepper, slice, tart, tea, yellow