Combine seasonings for pork rub (salt, pepper, cumin, paprika, and garlic powder) and massage onto the pork shoulder.
Heat oil in a large cast iron skillet over medium high heat. Sear pork shoulder on all sides until evenly browned.
Transfer meat to a slow cooker and add 10oz can verde enchilada sauce, then fill the can with water and add 10oz water to the crock pot.
Add the chopped onion, tomatillos, green onions, cilantro, garlic, poblano, and jalapeño.
Cook on low for 8 hours until meet is tender and shreds easily.
Remove meat and shred. Blend vegetables in the crock pot into a smooth verde sauce. Add meat back to sauce. Serve in a burrito, on nachos, or (my favorite) over rice with cabbage, cheese, avocado, and sour cream!