Preheat the oven to 425 degrees F. Oil a 3 or 4 cup ovenproof baking dish.
In a dry medium skillet, saute the chorizo over medium-high heat until almost crisp. Remove the chorizo to a plate. Add the onion and garlic to the pan juices and cook until soft, about 5 minutes. Return the chorizo to the skillet with the onions and garlic and stir to combine.
Put 1/2 of cheese in the baking dish and sprinkle with 1/2 of the chorizo mixture. Repeat with the remaining cheese and chorizo mixture. Bake until the cheese is bubbling, about 20 minutes. Serve with flour tortillas for soft tacos.