Trim the fat from 6-7 pounds of pork butt, leaving you with about 5 pounds of trimmed meat. Cut into medium sized chunks. Add 1 Tbsp kosher salt and 1/2 Tbsp black pepper. Toss to season meat. Cover with plastic wrap and let sit for 15-30 minutes as you prepare remaining ingredients.
Heat a large oven safe pot (i.e. enameled cast iron/dutch oven pot). Add 2 Tbsp canola oil and diced red onions and cook over medium high heat. Add 1/4 tsp kosher salt to sweat the onions. Cook until onions start to soften.
Add all the liquid juice of canned chipotle peppers to pot. Add half of peppers, or more depending on your spice level preference.
Discard the juice from tomato can. Crush all the tomatoes and add to the pot. Add whole peeled garlic cloves and 1 cup beer. Stir to combine. Add pork and bring to a boil, keep pot uncovered. As noted in picture above, some of the pork will be exposed. Not all the pork will be submerged in liquid. This will allow the pork to brown in the oven.
Preheat oven to 350 degrees F. Once mixture comes to boil, place pot in preheated oven. Bake for 3 hours. Rearrange and stir meat every hour to allow meat to brown.
When pork is done cooking, remove pork from sauce and place in a separate bowl. Using an immersion blender (or a standard blender) puree sauce until smooth.
Roughly shred pork and toss in smooth sauce. Serve pork on warmed corn tortilla with garnishes.