Cut pork into 1 inch cubes; season with salt and pepper. Heat oil in large skillet or Dutch oven. Add pork, onions, garlic powder, chili powder and chipotle chile powder; saute 3 to 5 minutes to brown the meat.
Add enough water to barely cover pork. Bring to a boil; cover, reduce heat and simmer 30 minutes. Remove lid and continue to simmer an additional 45 minutes or until liquid has evaporated.
Combine chopped tomatillos, tomatoes and cilantro in a small bowl.
Place an equal amount of pork on each tortilla. Top with tomatillo salsa.
