In a small bowl, stir together the chili powder, smoked paprika, cumin, oregano, onion powder, garlic powder, salt, and black pepper. Set aside.
Heat the oil in a large nonstick skillet over medium heat. Add the spice mixture and cook for about 1 minute, stirring constantly to toast the spices and bring out their flavor.
Stir in the tomato paste and water, mixing until the sauce is smooth. Let simmer for a couple of minutes until the sauce thickens.
Add the shredded rotisserie chicken to the skillet and toss until fully coated in the sauce. Let it cook for a few minutes until heated through. Taste and adjust seasoning if needed.
Warm the tortillas, then fill each with the chicken mixture. Top with smashed avocado, diced tomato, and a sprinkle of Cotija cheese.
Notes
If you’re prepping ahead, store shredded chicken in an airtight container in the fridge for up to 3 days or freeze it for up to 3 months.