Season cubed chicken with Adobo seasoning. Heat oil in large skillet. Add chicken, onions, garlic powder, chili powder, chipotle chili powder and cumin. Saute 3-5 minutes to brown the meat.
Add enough water to barely cover chicken. Bring to a boil; cover, reduce heat and simmer 30 minutes. Remove lid and continue to simmer an additional 15 -20 minutes, or until liquid has evaporated.
Combine chopped tomatillos, tomatoes, cilantro and juice of ½ lime in small bowl.
Place equal amounts of chicken on each tortilla. Top with salsa and avocado if desired.