Huevos Rancheros

Heat oil in a saucepan over medium heat. Add onion and garlic; cook 6 minutes. Add diced tomatoes with chiles, chipotle, cumin, and oregano. Bring to a boil, reduce heat and simmer, uncovered, 10 minutes; stir in tomato sauce and simmer 2 minutes. Remove from heat; cover. Warm refried beans in a saucepan over low heat; stir in cilantro. Cover and keep warm. Preheat oven to 225 degrees F. Place tostada shells directly on oven rack in oven. In each of 2 large skillets, melt 4 tsp butter over medium heat. When butter foams, add 4 eggs to each skillet. Cook until whites are firm and yolks are set but still soft, 2 to 3 minutes. To assemble: Place 2 warm tostada shells on each plate. Spread each with a little sauce, then with refried beans. Top with a fried egg and spoon some sauce over eggs. Sprinkle with shredded cheese. Surround with avocado slices and top eggs with salsa