Beef and Rice Stuffed Peppers

In a bowl, stir together the tomatoes, garlic, tomato paste, oregano, sugar, all but 1/4 cup of the scallions, and 1/2 teaspoon pepper. Transfer half of the mixture (about 1 cup) to a 5- to 6-quart slow cooker. Slice the tops off the peppers just below the stems. Roughly chop the tops and add them to the bowl with the remaining sauce, along with the beef, rice, raisins, and 1/2 teaspoon salt; mix to combine. Remove the ribs and seeds from the peppers. Slice a very thin piece from the base of each pepper so they sit upright and flat, but do not cut through. Season the inside of the peppers with 1/4 teaspoon each salt and pepper, then stuff with the beef mixture (about 1 cup per pepper). Transfer the peppers to the slow cooker, cover, and cook until the peppers are tender and the rice is cooked through, 3 to 4 hours on high or 5 hours on low. Transfer the peppers to plates. Stir the sauce to incorporate any excess liquid from the peppers. Spoon the sauce over the peppers and sprinkle with the feta and remaining scallions. Serve with a salad, if desired.