Season the pork with salt, garlic powder and pepper. Let sit for a few minutes.
Preheat 4 tablespoons of oil in a large, heavy skillet to medium for a few minutes.
Brown the pork as best you can on all sides in the hot oil.
Pour in 3 cups of warm water. Stir well, scraping the bottom of pan to get all those bits of flavor off the bottom. Cover with tight lid and continue cooking at heat right below medium for about 45-60 minutes or until the liquid evaporates.
While pork is cooking, add your tomatillos, jalapeños, onion and garlic to a pot of simmering water. Simmer for 10 minutes or just until tomatillos turn from bright green to olive green.
Using a slotted spoon, transfer salsa ingredients to the blender. Add cilantro and salt to taste. Blend on high until very smooth. Set aside.
Once all the liquid has evaporated from the pork, add the diced onion and garlic. Saute for 2 minutes. Pour in the salsa. Stir in the oregano and bay leaves. Reduce heat. If adding nopales, add them in right now. Cover and cook at a steady simmer for 20 minutes.