Sear the Chicken: Heat the a pan with some cooking spray over a medium-hot heat. Season the chicken pieces with salt and pepper, then add them to the hot skillet. Sear the chicken for about 2-3 minutes per side until lightly browned. Remove the chicken from the pan and set it aside.
Sauté Onions and Garlic: In the same pan, add the chopped onions and minced garlic. Sauté for about 2-3 minutes until they become fragrant and slightly translucent.
Add Seasonings and Tomatoes: Stir in all of the spices. Cook for another 1-2 minutes to toast the spices. Add the chopped tomatoes and diced green chili. Stir to combine.
Simmer the Chicken: Return the seared chicken pieces to the pan and pour in the chicken stock. Bring the mixture to a simmer.
Cook Low and Slow: Reduce the heat to low, cover the pan with a lid, and let the chicken simmer gently for about 20-25 minutes or until the chicken is cooked through and tender. Stir occasionally to ensure even cooking.
Shred the Chicken: Once the chicken is fully cooked, use two forks to shred it directly in the pan. The chicken should easily pull apart.
Serve or Store: Serve the Mexican Pulled Chicken or allow to cool and store portions.