In a large Dutch oven with a lid, cook the bacon over medium heat until crisp, about 4 minutes.
Add the sliced onions, cinnamon stick, bay leaves, and 1 teaspoon of the kosher salt. Cover and cook, stirring occasionally, until the onions are soft and tender, about 8 minutes.
Increase the heat to medium-high. Add the sliced red cabbage and cook, stirring, until wilted, about 8 minutes.
Stir in the apple, chicken broth, red wine vinegar, sugar, black pepper, and remaining salt to taste.
Cover and cook, stirring occasionally, until the cabbage is very tender, about 1 hour.
Uncover the pot, bring the mixture to a gentle boil, and cook until the liquid reduces to a sauce-like consistency, about 5 minutes.
Remove and discard the bay leaves and cinnamon stick.
Remove the pot from heat, cover, and let the cabbage rest for 20 minutes before serving to allow the flavors to fully develop.