Preheat the oven to 350 degrees F.
Place the fat back slices on a baking sheet and place in the oven. Bake until all the fat is rendered, 15 to 20 minutes. Set aside.
In a large pot over medium-high heat, add the onion, jalapeno, bell peppers
, vinegar and red pepper flakes
. Add 2 cups water, cover and cook until tender, 10 to 15 minutes.
Add the cabbage and cook until the cabbage
is just wilted, about 10 minutes. Season with the salt and black pepper and pour the rendered fat from the fat back over the cabbage mixture. Stir to combine and serve.