Slice your chicken breast into thin, uniform strips about 1/4-inch thick. Pat them dry with paper towels to ensure proper browning. Combine cumin, chili powder, paprika, cayenne, salt, and black pepper in a small bowl, then toss the chicken with half this spice mixture.
Heat olive oil in a large skillet over medium-high heat until shimmering. Add chicken strips and cook for 5-6 minutes without stirring until the bottom develops a golden crust. Stir and cook another 3-4 minutes until mostly cooked through. Transfer to a plate temporarily.
In the same skillet, add sliced peppers and onion along with minced garlic. Sauté for 4-5 minutes, stirring occasionally until vegetables soften and develop slight color. The peppers should still have a bit of crunch for textural contrast.
Return the sizzling chicken fajita skillet contents back to the pan along with remaining spice mixture. Pour in chicken broth and lime juice, stirring everything together. Simmer for 2-3 minutes until the liquid reduces slightly and flavors meld beautifully.
Remove from heat and stir in fresh cilantro. Taste and adjust salt and lime juice if needed. The dish should smell incredibly aromatic and taste vibrant, not heavy or overly spiced.