Make the seasoning. In a small bowl, mix chili powder, cumin, smoked paprika, garlic powder, onion powder, oregano, cayenne (if using), salt, and pepper. Set aside.
Prep the chicken. Pat the chicken dry. Slice breasts into cutlets or cube into bite-size pieces for faster cooking.
Toss with 1 tablespoon oil and the taco seasoning until evenly coated.
Cook the chicken. Heat a large skillet over medium-high and add the remaining 1 tablespoon oil. Cook chicken 4–6 minutes per side for cutlets or 6–8 minutes total for cubes, until browned and cooked through. Rest 3 minutes, then slice or shred.
Mix the lime dressing. In a jar or bowl, whisk olive oil, zest of 1 lime, juice of 2 limes, apple cider vinegar (optional), a pinch of salt, and black pepper.
Taste and adjust acid or salt.
Prep the veggies. Chop lettuce, dice bell pepper, halve tomatoes, slice red onion and jalapeño, dice avocado, and chop cilantro.
Assemble the bowls. Divide lettuce among 4 bowls. Top with chicken, bell pepper, tomatoes, red onion, avocado, cilantro, and cheese if using.
Add the finishing touches. Drizzle with lime dressing. Add a dollop of sour cream or Greek yogurt.
Finish with extra lime juice, salt, and pepper to taste.
Serve. Enjoy immediately while the chicken is warm and the lettuce is crisp.