Makes 4 servings.
4 tablespoons olive oil
8 garlic cloves, minced
½ small onion, finely chopped
½ pound small red or new potatoes, quartered
1 (14.5-ounce) can low-sodium diced tomatoes, with their juices
16 pimiento-stuffed low-salt Spanish olives, sliced (about ⅓ cup)
4 tablespoons finely chopped fresh parsley
4 (4-ounce) cod fillets, about 1 inch thick
Salt and freshly ground black pepper (optional)
In a 10-inch skillet, heat 2 tablespoons of the olive oil and the garlic over medium heat. Cook, being careful not to let the garlic burn, until it becomes fragrant, 1 to 2 minutes.
Raise the temperature to medium-high heat, and add the onion, potatoes, tomatoes with their juices, olives, and 3 tablespoons of the parsley. Bring to a boil. Reduce the heat to maintain a simmer, cover, and cook for 15 to 18 minutes, until the potatoes are tender. Transfer the mixture from the skillet to a large bowl; keep warm. Wipe out the skillet and return it to the stovetop.
Heat the remaining 2 tablespoons olive oil in the skillet over medium-high heat. Season the cod with salt and pepper, if desired, and add it to the pan. Cook for 2 to 3 minutes, then carefully flip the fish and cook for 2 to 3 minutes more, until the fish flakes easily with a fork.
Divide the tomato mixture evenly among four plates and top each with a cod fillet. Sprinkle evenly with the remaining 1 tablespoon parsley and serve.