For the shredded beef: Put the beef, lime juice, orange juice, chili powder, cumin, salt, coriander and garlic in a large Dutch oven, or heavy-bottomed pot, and add just enough water to cover. Bring to a boil, and then reduce to a simmer over medium-low heat and cook, covered, for 30 minutes. Remove the lid and continue cooking on a gentle simmer for 2 1/2 to 3 hours, stirring occasionally.
Once the beef is tender, let it cool slightly in the braising liquid and then shred with two forks, while still in the pot, so as to let all the shredded beef soak up the delicious sauce.
For the tomatillo guacamole: Combine the cilantro, tomatillos, garlic, avocado, jalapeno, onion, lime juice, cumin and salt in a food processor or blender and pulse until combined.
For the sopes: Combine the masa harina, flour, baking powder and salt in a mixing bowl. Make a well in the center and slowly add the warm water while incorporating the dry ingredients using a stiff spatula. Once the dough comes together, transfer it to a floured surface and knead it by hand until it is smooth and not crumbly, about 5 minutes.
Roll the dough to 1/4-inch thickness and then cut it into 2-inch circles with a biscuit cutter or the rim of a glass; you should get 36 circles. Re-roll and re-cut scraps of dough until all of it is used. Create a ridge around the edge of each sope using your thumb, and working from the center outwards. You are trying to make a small well for the toppings to rest in once the dough is fried.
Fill a cast-iron skillet with 1 1/2 inches of vegetable oil and heat to 350 degrees F over medium-high heat. Once the oil is hot, fry the sopes until their edges are crispy and just starting to brown, about 3 minutes. Flip and cook for another 3 minutes. Transfer the sopes to a paper-towel-lined plate and season with salt as they come out of the oil.
For the toppings: Melt the butter in a skillet, then add the refried beans. Stir to warm through and loosen the mixture. Set aside. Mix the pickled jalapenos and tomatoes and set them aside.
Fill each sope with a layer of beans, followed by some shredded beef and a little tomatillo guacamole. Top each with some of the cabbage, tomato-jalapeno mixture, crema, cotija and cilantro.