Heat 1 tablespoon olive oil in a large skillet over medium-high heat until shimmering. Add 1 pound lean ground beef and 1 diced small yellow onion. Season with ½ teaspoon kosher salt and ¼ teaspoon black pepper. Cook, breaking up the meat into small pieces, until the beef is cooked through and no longer pink, 6 to 8 minutes. Drain off any excess fat, then transfer to a 4-quart or larger slow cooker.
Add 1 ½ cups cottage cheese, 1 (15-ounce) can tomato sauce, 1 (14.5-ounce) can low-sodium beef broth, 1 diced medium red bell pepper, 2 tablespoons dried Italian seasoning, and 1 teaspoon garlic powder. (For a smoother sauce, blend the cottage cheese and tomato sauce together in a blender or food processor until smooth before adding to the slow cooker.) Stir to combine.
Cover and cook for 4 to 6 hours on the LOW setting, or 2 to 4 hours on the HIGH setting. About 30 minutes before it is ready, stir in 8 ounces shredded sharp cheddar cheese and 6 ounces dried elbow macaroni. Cover and cook until the noodles are tender. Stir to combine. Taste and season with more kosher salt as needed. Garnish with chopped fresh parsley leaves if desired.
