Remove any damaged outer leaves from the cabbage. Cut out the tough core and roughly chop the cabbage into bite-sized pieces. Set aside.

Heat a large skillet or cast-iron pan over medium-high heat. Add the ground beef and break it apart with a wooden spoon or spatula. Cook for about 5 to 7 minutes, stirring occasionally, until browned. If there is excessive grease in the skillet, drain some of it while leaving a small amount for flavor.

Push the ground beef toward one side of the skillet. Add the chopped onion to the open side. Cook for approximately 3 to 4 minutes, or until the onion begins to soften and become translucent. Mix the onions into the ground beef.

Add the minced garlic. Cook for another 30 seconds to 1 minute, stirring frequently, until fragrant. Be careful not to burn the garlic.

Pour the entire can of diced tomatoes, including the juices, into the skillet. Add the beef bouillon powder, cumin, smoked paprika, cayenne pepper, salt, and black pepper if using. Stir everything together until well combined. Bring the mixture to a gentle simmer and cook for approximately 5 minutes.

Add the chopped cabbage to the skillet. Don't worry if the skillet looks extremely full. The cabbage will reduce significantly as it cooks. Carefully toss the cabbage with the beef and tomato mixture.

Reduce the heat to medium-low and cover the skillet. Cook for approximately 10 to 15 minutes, stirring every few minutes so the cabbage cooks evenly. For firmer cabbage, stay closer to 10 minutes. For softer cabbage, cook closer to 15 to 20 minutes.

Remove the lid and stir everything together. Taste and add additional salt, pepper, cayenne, or bouillon as needed. If there's more liquid than you want, leave the skillet uncovered and simmer for another 3 to 5 minutes to reduce the sauce.

Sprinkle with red pepper flakes if you want additional heat. Serve hot straight from the skillet.