Pat the pork shoulder dry with paper towels, then sprinkle with a liberal amount of salt and pepper on all sides, including the skin side.
Preheat the oven to 350 degrees Fahrenheit. Let the pork shoulder sit at room temperature while the oven preheats.
When the oven is preheated, place a heavy bottomed lidded pot (I used my enameled cast iron dutch oven) on the stove top. Add 2 tablespoons of grapeseed oil and warm over high heat. When the oil is shimmering, add the pork shoulder, fat side down, and cook on that side until nicely golden brown. Rotate the pork to the next side, and continue, until all the sides and end pieces are nicely browned.
When the pork is browned all over, rotate the pork so the skin side is facing up, and place the lid on the pot. Put the dutch oven inside the oven, and let cook without moving for about 4 hours, until the outside of the pork is deeply browned, and the meat is fall apart tender. If the skin is not yet dark brown and crispy, increase the heat to 500 degrees and let cook with the lid off the pan, until it is crispy.
Remove from the oven, and let the pork rest for 30 minutes. Remove the crispy skin and set aside. Then, use two large forks or your fingers to pull the pork apart into pieces and then shred into bite-sized pieces. Chop the crispy skin into small pieces and toss into the shredded meat as well.
Next, add 2 tablespoons of grapeseed oil to a large skillet and warm over high heat. Add the shredded pork & let it cook for a few minutes without stirring until some of the pieces get nice and crispy. Remove from the skillet into a serving bowl.
Next, in a small skillet, pour enough grapeseed oil to form a thin layer in the pan. Warm over high heat. Using tongs, add one corn tortilla to the pan. Let it cook briefly on one side until the tortilla starts to puff up. Flip over and cook briefly on the other side until lightly golden but still pliable. Remove to a paper towel lined plate and continue with the desired number of tortillas (16 or 20 should be perfect). Continue to add oil as needed to keep a light coating in the pan.
When the tortillas are done, you're ready to assemble the tacos! Place some of the pork carnitas in the center of a tortilla, spoon some salsa verde over the top, and sprinkle with minced onion and cilantro. Squeeze fresh lime over the top and serve right away.