Heat olive oil in a large heavy pot or a 6-quart Dutch oven over medium heat. Cook and stir onion in hot oil until translucent, about 5 minutes.
Break ground beef into small chunks and add to the pot; cook and stir, continuing to break the beef into smaller pieces, until the beef is completely browned, 5 to 7 minutes.
Season beef mixture with garlic powder, red pepper flakes, Italian seasoning, and a dash of salt. Stir cabbage, diced tomatoes, and tomato sauce with the beef mixture; bring to a boil, reduce heat to low, and cook mixture at a simmer until cabbage is fork-tender, about 25 minutes. Season with salt and pepper. Serve with cheddar cornbread and dinner salad.