Serve as a condiment, use as a tart filling or even add it to bread dough — see Onion Nigella Bread. Caramelised onion is especially good made with the sweet, golden Kununurra onions from the Kimberley region of Western Australia, which appear in spring.
Cook onion in a good quantity of olive oil in a wide, heavy-based pan over moderate heat until onion caramelises and tastes sweet. Strain, reserving flavoured oil for other cooking. Refrigerate for up to 2 weeks.