Tuna with Slow-Cooked Onions (Atún Encebollado)

Name: Restaurante Casa Bigote
Address: C. Pórtico Bajo de Guía, 10, 11540 Sanlúcar de Barrameda, Cádiz, Spain, Sanlúcar de Barrameda, ES

Tender pieces of tuna stewed in an aromatic broth with poached onion, served directly in a traditional clay pot.

The tapas dictionary

Encebollado: Cooked with plenty of onion, slowly softened until it turns sweet and silky.