Cebolada

Cebolada is a Portuguese onion stew, onion sauce or paste that is prepared with onion as a primary ingredient. Versions prepared as a paste may be slow-cooked. It may accompany various dishes, such as seafood dishes prepared with swordfish steak. Atum de cebolada is a dish prepared with tuna steak and cebolada that is prepared with caramelized onions. Cebolada is used on beef dishes such as bifes de cebolada , which uses thinly-sliced steak and cebolada. Additional ingredients in the dish's preparation include white wine, vinegar and butter. Bifes de cebolada is a frequent menu item in Portuguese restaurants, and traditionally it is served with Portuguese fried potatoes.

Source: Wikipedia