Remove outer cabbage leaves, cut into quarters, and slice each quarter into 1-inch strips.

Slice the onion into thin rings and mince the garlic cloves.

Heat a large skillet over medium heat and add the butter, allowing it to melt and coat the pan, about 1 minute.

Add the sliced onion to the skillet and sauté for about 3 minutes until translucent.

Stir in the minced garlic and cook for an additional 1 minute, ensuring it does not burn.

Add the chopped cabbage to the skillet, stirring to combine with the onion and garlic.

Season with salt, pepper, and red pepper flakes if desired, then cook for about 10 minutes, stirring occasionally, until the cabbage is tender and slightly caramelized.

If desired, add 1 tablespoon of balsamic vinegar in the last minute of cooking for a touch of sweetness.

Serve the fried cabbage warm for best flavor and texture.