Classic Stuffed Peppers

Preheat oven to 400°. In a small saucepan, prepare rice according to package instructions. In a large skillet over medium heat, heat oil. Cook onion until soft, about 5 minutes. Stir in tomato paste and garlic and cook until fragrant, about 1 minute more. Add ground beef and cook, breaking up meat with a wooden spoon, until no longer pink, 6 minutes. Drain fat. Return beef mixture to skillet, then stir in cooked rice and diced tomatoes. Season with oregano, salt, and pepper. Let simmer until liquid has reduced slightly, about 5 minutes. Place peppers cut side-up in a 9"-x-13" baking dish and drizzle with oil. Spoon beef mixture into each pepper and top with Monterey jack, then cover baking dish with foil. Bake until peppers are tender, about 35 minutes. Uncover and bake until cheese is bubbly, 10 minutes more. Garnish with parsley before serving.