Cook pasta in salted boiling water until 1 minute shy of al dente. Drain and set aside, reserving ½ cup pasta water.

Heat 2 tablespoons olive oil in a large skillet over medium-high heat. Pat chicken strips dry with paper towels, season both sides with half the fajita seasoning, and add to the hot pan in a single layer. Sear without moving for 3 minutes, flip once, and cook another 3-4 minutes until browned and cooked through. Transfer chicken to a plate.

Add sliced bell peppers and onion to the same skillet. Sauté 4-5 minutes until softened but still slightly crisp, stirring occasionally. Add minced garlic in the last 30 seconds and cook until fragrant.

Lower heat to medium and stir in remaining fajita seasoning, then pour in chicken broth. Bring to a simmer and scrape up any browned bits stuck to the pan. Remove from heat and stir in sour cream until smooth and combined.

Return chicken and cooked pasta to the skillet. Toss everything together over low heat for 1-2 minutes until pasta is coated and sauce thickens slightly. Squeeze fresh lime juice over the top and garnish with cilantro or green onions.