Onions

Raw onion rarely finishes cooking

A focaccia bakes fast, and that is not enough time to tame a pile of raw onion — it emerges sharp, crunchy, and harsh rather than the sweet, soft topping most people picture. This is the most common onion disappointment. Thin raw slices soften a little and can work as an accent, but for a proper onion focaccia you cook the onion first.

Caramelized and softened onions

Cooking onion low and slow in olive oil until deeply golden and jammy concentrates its sugars into a sweet, savory topping that needs only to warm through on the focaccia. This is the backbone of a great caramelized-onion focaccia. Even a quicker sauté until soft and translucent (without full browning) transforms the flavor and texture versus raw.

Season the onions as they cook, and cool them before topping so they do not slump the proofed dough. Spread them evenly and press lightly into the dimples.

Which onions to use

Yellow onions are the all-rounder and caramelize beautifully. Red onions are milder and prettier, good thinly sliced (and quick-pickled red onion is a bright raw-style garnish added after baking). Sweet onions cook down especially soft. Shallots are refined and jammy for a smaller batch. Scallions and spring onions are mild enough to use raw or barely cooked.

Buying and storing

Choose firm, dry onions with tight papery skins and no soft spots or sprouting. Store them cool, dark, dry, and airy — never bagged in the fridge — and keep them away from potatoes, since each speeds the other’s spoiling. A cut onion should be wrapped and refrigerated and used within a few days.