For the spicy salsa, roast the Roma tomato, tomatoes, onion, garlic cloves, and serrano peppers. Blend them in a blender and add salt to taste. Set aside.

In a mixing bowl, add the masa harina, a pinch of salt, and gradually add water until you get a smooth, uniform dough.

Remove the cooked potatoes and, in the remaining hot water, soak the chorizo briefly to remove the casing.

Add the chorizo to a hot skillet and cook until browned. Add the potatoes, cut into small cubes. Season with salt and mash the potatoes slightly so they mix well with the chorizo.

To assemble, spread a layer of refried black beans on each sope, then add the chorizo and potato mixture, shredded lettuce, sour cream, and salsa.