Heat your oven to 350°F. While it preheats, heat a large skillet over medium-high heat and add the ground beef, breaking it apart with a spoon as it cooks. Cook for 5 to 7 minutes until the beef is no longer pink, then drain off the excess fat by tilting the skillet and pressing the meat against the side with a spoon. Set the cooked beef aside on a plate.

In a large bowl, combine the coarsely chopped cabbage, tomato sauce, diced onion, uncooked rice, salt, garlic powder, and black pepper. Add the cooked ground beef from Step 1 and stir everything together until well mixed. I like to use a large spoon to gently fold rather than stir aggressively—this helps the cabbage stay slightly intact rather than getting bruised, which keeps the final texture more interesting.

Pour the casserole mixture from Step 2 into a 9x13 inch baking dish, spreading it out evenly. Pour the beef broth over the entire mixture, making sure it's distributed throughout. The liquid should partially submerge the ingredients—this allows the rice and cabbage to cook evenly and absorb all those savory flavors.

Cover the baking dish tightly with foil and place it in the preheated 350°F oven. Bake for 1 hour without lifting the lid. After 1 hour, carefully remove the dish from the oven and give the casserole a good stir to redistribute the rice and ensure even cooking. Re-cover with foil and return to the oven for another 20 to 30 minutes, until the rice is tender and most of the liquid has been absorbed. I find the final texture is best when there's just a little liquid left at the bottom—this keeps everything moist without being soupy.