In a large bowl, combine the marinade ingredients: 2 tbsp olive oil, lime juice, chili powder, cumin, smoked paprika, garlic powder, oregano, salt, and pepper. Whisk until well combined.

Add the sliced chicken to the bowl and toss thoroughly to ensure every piece is coated. Let the chicken marinate for at least 15 minutes at room temperature, or up to 4 hours in the refrigerator for more flavor.

Heat a large cast-iron skillet or heavy-bottomed pan over medium-high heat until it's very hot. Add the marinated chicken to the skillet in a single layer (work in batches if necessary to avoid overcrowding). Cook for 3-4 minutes per side, until browned and cooked through. Remove the chicken from the skillet and set it aside on a plate.

Reduce the heat to medium. Add the remaining 1 tbsp of olive oil to the same skillet. Add the sliced onions and bell peppers. Sauté, stirring occasionally, for 6-8 minutes, or until the vegetables are softened but still have a slight crispness (crisp-tender). Scrape up any browned bits from the bottom of the pan as they cook.

Return the cooked chicken to the skillet with the vegetables. Toss everything together and cook for another 1-2 minutes until heated through.

Serve the sizzling chicken and vegetable mixture immediately with warm tortillas and your favorite toppings like sour cream, guacamole, pico de gallo, and shredded cheese.