Heat oven to 375°F. Lightly grease a 9x13-inch baking dish.
Season chicken with 1 tablespoon fajita seasoning, salt, and pepper. Toss to coat.
Warm 1 tablespoon olive oil in a large skillet over medium-high. Sear chicken until just cooked, 4–6 minutes. Transfer to a bowl.
Add remaining oil to the skillet. Sauté onion and bell peppers until crisp-tender, about 5 minutes. Stir in garlic for 30 seconds.
Lower heat. Melt in cream cheese, then whisk in sour cream, broth, remaining fajita seasoning, and the drained tomatoes. Simmer until smooth and creamy.
Fold chicken back into the skillet with lime juice and 1 cup shredded cheese. Stir to coat evenly.
Spread mixture in the baking dish. Top with remaining cheese.
Bake until bubbling and lightly golden, 12–15 minutes. Rest 5 minutes, then garnish with cilantro and serve.