Heat 1 1/2 tablespoons of olive oil in a large skillet or Dutch oven over medium-high heat. Add the chicken pieces and season with half of the fajita seasoning. Cook the chicken for about 2 minutes before stirring or flipping to cook for an additional 1-2 minutes until lightly browned; then remove and set aside.
Add the remaining 1 1/2 tablespoons olive oil to the pan, then toss in the diced onion and sliced peppers along with the rest of the fajita seasoning. Cook, stirring occasionally, until the vegetables soften and develop some charred spots, about 4-5 minutes. Stir in the minced garlic and cook for 30 seconds before removing the vegetables to join the chicken.
Pour in the chicken stock, heavy cream, diced tomatoes with chiles, and add the pasta along with a pinch of salt and pepper. Scrape the bottom of the pan gently to lift any browned bits, then bring everything to a boil. Lower the heat to a gentle boil, cover, and cook for around 15 minutes, stirring sometimes.
Check if most of the liquid has been absorbed; if not, continue cooking for 3-5 more minutes. Return the cooked chicken and veggies to the pot and stir until warmed through.
Serve the pasta topped with sliced green onions, fresh cilantro or parsley, and finish with a squeeze of fresh lime juice for a bright flavor.
