Heat a large skillet over medium-medium high heat. This recipe works better in a stainless steel skillet rather than a non stick.
When pan is hot, add olive oil. Allow oil to get hot, then add the onions. Season with salt. Cook the onions, stirring as needed, until they are soft and starting to caramelize. Add the garlic and sauté for 30 seconds.
Add the cabbage. You will need to do this in 2-3 batches depending on how much cabbage you have and the size of your pan. Add about half of the cabbage and use a spatula to carefully mix it in with the onions. Allow to sit undisturbed for a few minutes, until cabbage is starting to brown on the bottom. Then use a metal spatula to turn the cabbage so that the other side can brown.
Add the 1 tablespoon of butter, a bit more salt, pepper to taste and a pinch of red pepper flakes, use the spatula to mix.
Add the rest of the cabbage and mix it in. Allow it to sit again for a few minutes to let the bottom start to caramelize. When it does, flip with spatula.
When cabbage is soft and slightly caramelized, remove from heat. Taste and season with more salt and pepper if desired. Serve.