If adding beef, heat a large pot or Dutch oven over medium heat. Add the ground beef, sprinkle with a pinch of salt, and break apart with a wooden spoon. Cook until no longer pink, stirring occasionally.
Add the onion and cook an additional 1-2 minutes to soften. Add the bell pepper, celery, carrots, cabbage, diced tomatoes, red pepper flakes, garlic powder, salt, and stock, stirring to combine.
Cover, bring to a boil, then reduce to a simmer. Simmer on low, covered, for 25-30 minutes, or until the vegetables are tender.
Uncover, stir, and taste, adding additional salt or red pepper flakes if desired