Slice the chicken breasts thinly, about paper-thin, to ensure quick, even cooking and juiciness.
Heat your large skillet over medium-high heat and add a tablespoon of oil, shimmering as it warms up and begins to smell nutty.
Add the sliced chicken to the hot pan in a single layer, cooking in batches if necessary. Let it sear until golden brown on the edges and cooked through, about 3-4 minutes per side. Remove and set aside.
In the same pan, toss in the sliced bell peppers and onions. Cook, stirring occasionally, until they’re tender but still vibrant, with some caramelized spots, about 5-7 minutes.
Return the cooked chicken to the skillet with the vegetables. Sprinkle the fajita spice blend evenly over everything and toss to coat, cooking for another 2 minutes until fragrant and heated through.
While the filling cooks, warm the tortillas in a dry skillet or microwave until soft and pliable, about 20-30 seconds.
Scoop generous portions of the chicken and vegetable mixture into each warm tortilla. Garnish with chopped cilantro and squeeze fresh lime over the filling for bright, zesty flavor.
Serve immediately with optional dollops of sour cream or crema on the side for added creaminess.
