Step 1Roast ancho and guajillo chiles in dry skillet over medium heat until fragrant and softened, about 5 minutes. Slice open and remove seeds and veins.
Step 2Heat water in 6-quart saucepan over medium heat and add chiles. Simmer 20 minutes. Drain chiles; reserve water.
Step 3In blender or food processor, puree chiles, garlic, onions, cumin seeds, ginger, oregano, cloves, allspice, cinnamon, thyme, bay leaves, salt and vinegar in batches to form thick paste. If too thick, add a little cooking water.
Step 1Cut banana leaf into 6 to 8 pieces small enough to fit into deep-sided roasting pan. Brush pieces with oil, stack and wrap them in foil. Roast at 425 degrees until leaf pieces are soft and pliable, 15 minutes.
Step 2Coat lamb with lard, making sure pieces are well covered. Let stand 30 minutes.
Step 3Spread Adobo Paste over chunks, working it into lamb so all pieces are covered. Let stand 30 minutes.
Step 4Line bottom and sides of deep-sided roasting pan with most of roasted banana leaf pieces. Place lamb chunks on top. Cover with remaining leaf pieces.
Step 5Place foil on work surface and roll masa out so it's large enough to cover lamb and leaf pieces and just fit inside roasting pan. Lift foil and invert masa onto leaf pieces, then peel away foil. Cover pan with lid.
Step 6Fill shallow pan with water and place on lower oven rack so it will be beneath roasting pan. Bake lamb at 350 degrees until tender, 3 to 4 hours. Start checking lamb after 3 hours by carefully lifting edge of masa to remove meat chunk; if lamb is not tender, pack masa back around lamb and continue to cook, checking again after 10 to 15 minutes.
Step 1Place tomatoes in baking dish and roast at 425 degrees until tender and slightly charred, about 45 minutes.
Step 2When tomatoes are cool enough to handle, blend tomatoes, garlic, onions and oregano in blender until smooth, in batches, if necessary.
Step 3Heat oil in large saucepan over high heat and cook tomato mixture 5 minutes, stirring frequently. Add broth. Season to taste with salt, if necessary. Simmer soup 30 minutes to meld flavors.
Step 1Remove lamb from oven. Uncover and discard masa and leaves.
Step 2Shred lamb with 2 forks while still hot. Drain pan juices and add to Soup.
Step 3To serve, divide shredded lamb among 10 to 12 soup bowls and pour Soup over. Garnish with onions, cilantro and limes.