Season chicken with salt and pepper.
In a large straight sided skillet (with a lid) heat oil over medium-high heat. Add chicken and sear on both sides, about 2 minutes a side.
Add onion to chicken and cook about 5 minutes or until soft.
Stir in tomatoes, chili powder, cumin, cayenne, oregano, vinegar and garlic.
Reduce heat to medium-low and cover. Cook about 15 minutes until the chicken is cooked through, stirring every few minutes.
Remove chicken to cutting board. Using two forks shred the chicken. Return shredded chicken to skillet.
Add lime juice and season with salt and pepper.
Allow to simmer until chicken has absorbed most of the liquid. At this point you can serve or cover and reduce heat to low and allow to sit until you are ready to serve. If the chicken looks to dry when ready to serve just add a 1/4 cup of water and bring back to temperature.