Put the drained beans and chicken broth in a large bowl.
In a saute pan, heat the olive oil over medium-high heat. Add the onion, tomato, chile, and garlic. Saute until the onion is soft, about 5 minutes. Rub the oregano, between palms of your hands and sprinkle over the beans. Add salt and pepper, to taste. Add the beans and broth to the pan and simmer for 10 minutes. Cool the beans for about 5 minutes before putting them in the blender. Carefully, pour the mixture into a blender and puree. Return the pureed mixture to the pan and gently reheat over medium-low heat, stirring frequently.
Using tongs, pass the tortillas 1 by 1 through the refried bean sauce until they are somewhat softened and coated on both sides with the sauce. Set aside on a plate. Fill each tortilla with 1/4 cup of shredded cheese. Fold in half and arrange them, overlapping, in a 9 by 13-inch baking dish. Top with an additional 1 to 1 1/2 cups of the bean sauce, just enough to cover the beans but allow the edges of the folded tortillas to show. Bake until cheese is melted about 10 to 15 minutes.
To serve, drizzle with Mexican sour cream lengthwise in a 2-inch thick strip down the center of the dish. Top with 8 overlapping red onion rings.