Thinly slice two sweet yellow onions and shred half a head of green cabbage into uniform strips for even cooking.

Warm a large skillet over medium heat. Add 1 tablespoon olive oil and 1 tablespoon butter until foam subsides.

Add onions, reduce heat to medium-low, and cook stirring every few minutes until deep golden brown, about 20–25 minutes.

Stir in 2 minced garlic cloves and cook for 1 minute until fragrant.

Increase heat to medium, add cabbage, ½ teaspoon salt, and ¼ teaspoon black pepper. Sauté until tender-crisp, about 8–10 minutes.

Drizzle 1 tablespoon apple cider vinegar over the skillet. Stir and cook 2 more minutes to deglaze.

Taste and adjust salt or pepper as desired, then transfer to a serving dish while piping hot.