Heat the oil in a medium skillet over medium heat. When the oil is hot, fry the tortillas, 1 at a time, on both sides until they are crisp. Remove from the oil and drain on a sheet tray lined with a brown paper bag or paper towels.
Preheat the broiler.
Put the fried tortillas on a sheet tray and top each with 1/4 of the bean mixture and 1/4 of the cheese. Put under the broiler until the cheese is melted and bubbling, about 2 minutes.
In a medium bowl mix together the tomato, onion, and chili powder, and season with salt, to taste.
Remove the tortillas from the sheet tray to individual serving dishes and top with shredded cabbage, the tomato mixture, and a tablespoon of sour cream.