Stem and seed the dried chiles, then pour boiling water over them. Let them soften while you chop the other vegetables.
Get a comal or cast iron pan hot, and lay the onion and tomatoes, cut side down. Scatter the garlic cloves around the edge of the pan. Let them blacken a bit, which should take about 6 to 10 minutes. Turn the garlic cloves after about 5 minutes. Use a metal spatula to turn the onion and tomatoes, scraping all the blackened and browned bits. Move those bits to the blender.
While this is happening, toast the cumin, black peppercorns and cloves in a dry pan until you can smell them. Grind them in a spice grinder and put the powder into the blender. Put the tablespoon of salt, bay leaves and oregano into the blender, too.
When the vegetables are nicely charred, put them in the blender. Tear the chiles into pieces and add them to the blender, along with a healthy glug of their soaking water. Puree this, adding the beer and vinegar as you go. You want it pretty smooth.
Coat the meat with this sauce, put it all into a covered container and let it sit overnight, or at the very least an hour.
When you are ready to cook, preheat the oven to 275°F. Line a heavy, lidded pot like a Dutch oven with banana leaves and put the meat in the center. Add the remaining marinade. Wrap the meat up as best you can with the leaves, then put the lid on.
Mix the masa or flour with water until you have a clay-like paste. Jam it all around the seal between the lid and the pot, and put the pot in the oven. Let it cook for at least 4 hours before checking, no matter what. I don't check until 8 hours have passed. You want the meat to be falling apart.
When you are ready, move the meat to a large bowl and pour all the broth over it. Pull the meat into largish pieces and give everyone some. Let them make their own tacos as they wish, or completely shred the meat and just make tacos. Garnish with the cilantro and chopped onion soaked in lime juice.
NOTE: If you have smoked salt, use that. It adds a nice touch to the meat.