Heat the oil in a large saucepan over medium heat. Add the onion and cook until softened, about 5 minutes. Add the olives, orange segments, and tomatoes. Cover and simmer for 10 minutes. Add the salt, pepper, and halibut to the pan. Spoon the sauce over the halibut. Cover and simmer until cooked through, about 7 minutes. Divide the halibut and sauce among individual plates and sprinkle with the dill.
Tip: Try this bold combination of flavors and colors with other seafood, including cod, shrimp, and salmon.