To prepare the cabbage, first remove the outer leaves. Then, cut the cabbage in half from the top down through the core. Place the cut side down on your cutting board and slice into about 1 inch wide strips around the core. Then, chop the strips into about 1 inch pieces. Discard the core.
To a large skillet on medium-low heat add the chopped bacon and cook until crispy, stirring occasionally, about 8-10 minutes. Remove the bacon from the pan to a paper towel lined plate.
Leave the bacon drippings in the pan and add 2 tbsp unsalted butter.
Add the cabbage to the pan and turn to medium high heat and sauté 8-12 mins, stirring occasionally until the cabbage is tender and begins to brown / caramelize.
When done, add the apple cider vinegar, salt, chili flakes and few turns of ground pepper, stir to combine and cook for one more minute. Remove from the heat and adjust seasoning with red pepper flakes, salt and pepper to your liking.