In a large skillet or saucepan, heat the oil with the garlic over moderate heat. When the garlic sizzles, add the tomatoes, crushing them with your hands, and stir in the fish stock, lemon juice, tomato paste, sugar and bay leaf.
Simmer for 7 to 10 minutes, until thick but still fairly liquid. Then stir in the scallops and the spinach and continue simmering until the scallops are cooked through and the sauce is thick, 3 to 5 minutes more. Serve over cooked pasta -- suggestions: spaghetti, linguine, or fettuccine.