In a dutch oven, heat the olive oil under medium high heat. Add onions and cook until softened, about 5 minutes or so.
Stir in cumin, chili powder, salt and pepper.
Add in chicken in one layer, then top with salsa and chicken stock. Cover and cook for about 15 minutes, or until chicken is cooked through. (You could honestly cook for longer if you're using chicken thighs because it's practically impossible to overcook them).
Remove the chicken and let cool on a cutting board for about 5-10 minutes. Continue to heat sauce under medium heat.
Shred chicken with forks and add back into sauce. Stir in lime juice. Season with salt and pepper to taste, if needed.
Assemble tacos any way you like, we like adding some shredded cheddar cheese, pickled jalapenos, and sour cream.