While the peppers are roasting, add the oil, onions, and spice mix to a skillet heated over medium. Cook for about 5 minutes until the onions begin to soften. Then add the cauliflower and cook for an additional 5 minutes until the cauliflower begins to soften as well.
Once the peppers are cool enough to handle, make a slit in each pepper and remove the seeds and ribs. Then fill each pepper with the chorizo and cauliflower mixture, dividing it evenly among the four peppers. Place each pepper side by side in a baking dish and sprinkle with 1/2 cup of cheese.