In a large skillet over medium heat, warm the fat until it has melted. Add half of the beans and 1/4 cup of the broth. Using a potato masher, smash the beans. Add the remaining beans and the rest of the broth and mash again. Stir in the cumin and oregano. Cook until most of the liquid has evaporated and the beans are a creamy consistency. Add a little water if they look too dry. If using, incorporate the chorizo and continue to cook until warmed through. Set the refried beans aside.

Preheat the oven to 450°F.

Separate the onion slices and place them in a small bowl. Sprinkle the salt over the slices and squeeze the lemon juice over them. Toss to coat evenly with the salt and lime. Allow the onions to rest for 5 minutes. Drain any excess liquid and set the onions aside.

Take a broiler-safe baking tray or dish and spread the refried beans into an even layer on the bottom. Scatter the cheese over the top then add the onions and olives. Place the pan in the oven and bake until the beans and cheese are bubbling.

Turn the oven up to broil and cook just until the cheese and onions have browned but are not charred.

Remove the pan or dish from the oven and arrange the tomatoes and avocado slices on top. Scatter cilantro over the tomatoes and avocado. Then, spoon some sour cream on top of the produce and scatter the jalapenos over the cream, if desired. Place tortilla chips all around the perimeter and have an extra bowl of them. Serve lime wedges on the side.