1. Preheat the oven to 425 degrees F.
2. In a oven-safe skillet, brown the chorizo until cooked through, Break into small crumbles with a spatula as it cooks. Set aside, leaving the drippings in the pan.
3. Reduce the heat to medium.
4. Add the onion and coat with the drippings left in the pan. Season with salt.
5. Over low heat, stirring occasionally, cook the onions until they have softened and caramelized all over.