In a large skillet over high heat put 1/2 cup olive oil, add the onions garlic, and thyme. Allow the onions to cook for 6 minutes.
Cut the salt fish into 1-inch pieces, and add them to the pot. Cook for 5 minutes, add the tomatoes, and the rest of the oil. Season with salt and pepper, to taste, and let simmer for 15 minutes more. Garnish with sliced scallions.