Preheat oven to 325ºF.

Pour the olive oil into a large Dutch oven (or other large, heavy pot with a lid); add the onions and half a teaspoon of salt and cook over medium heat until soft and light golden brown, at least 20 minutes.

As the onions cook, slice the cabbage in half through the core and remove it by making wedge-shaped cuts in each half; if the exposed end of the core is dry and woody, trim it off and discard.

Finely chop whatever’s left of the core and add to the pot to cook with the onions and oil.

Shred the cabbage leaves as finely as you can, and set them aside.

When the onions and cabbage core have gotten nice and brown, stir in the garlic and plenty of black pepper. Let them sizzle for about a minute, until the garlic barely starts to brown and the pepper is super fragrant, then add the shredded cabbage leaves.

Stir and toss gently to coat every single shred of cabbage with oil.

Add the vinegar and another big pinch of salt, stir again, and cover the pot.

Transfer the pot to the oven and roast for 1 to 1 ½ hours (or more) stirring once or twice.

Before serving, add more salt, pepper, and vinegar to taste—you’ll be surprised at how much salt this dish can soak up, so don’t be shy with the seasoning.

This is a thoroughly beige dish, so feel free to perk things up with a squeeze of lemon and a scattering of fresh herbs if you like.