Fry bacon in a large skillet over medium-high heat until crispy, about 5 minutes. Remove bacon from skillet and drain on a plate lined with paper towels; reserve bacon grease in the skillet. Crumble bacon into a bowl when cool and set aside.

Add onion, celery, and red bell pepper to the bacon grease in the skillet. Cook over medium heat until softened, about 3 minutes. Add cayenne, parsley, mustard, and black pepper and cook 2 minutes. Add cabbage; cover and cook 10 minutes. Uncover, increase heat to high, and cook, stirring often, until cabbage is wilted and tender, about 10 additional minutes.

Add apple cider vinegar and reserved crumbled bacon to the skillet and toss to coat. Serve immediately.