Step 1Heat the oven to 425 degrees.
Step 2Place the red onion in a small bowl and cover with the vinegar, pressing down the onion to submerge if needed. Let stand until ready to serve.
Step 3Heat a large cast iron or other heavy skillet over medium-high heat. Crumble the chorizo into the skillet and cook, stirring and breaking into almond-sized chunks, until cooked through and crisp, about 5 minutes. Transfer to a bowl. Add the beans to the skillet and cook, stirring and scraping up any browned bits from the pan, until heated through, 2 to 3 minutes.
Step 4Divide the beans among the tortillas and spread in a thin, even layer, leaving ½-inch rim. Bake on ungreased baking sheets until the tortilla is crisp and lightly browned around the edges, about 8 minutes. Sprinkle the chorizo and cheese on top and return to the oven. Bake until the cheese just melts, 1 to 2 minutes.
Step 5Cut in wedges and top with the cabbage. Drain the onions and scatter on top. Serve hot.