Chicken Fajitas

In a large bowl, whisk lime juice, chili powder, red pepper flakes, ¼ cup oil, and 1 tsp. cumin. Season chicken with salt and pepper, then add to bowl and toss to coat. Cover and refrigerate at least 30 minutes and up to 2 hours.

In a large skillet over medium heat, heat remaining 1 Tbsp. oil. Add chicken and cook, turning occasionally, until golden brown and an instant-read thermometer inserted into thickest part registers 160°, about 8 minutes per side. Transfer to a cutting board. Let rest 10 minutes, then slice into strips. 

Meanwhile, in same skillet over medium heat, combine peppers, onion, and remaining 1 tsp. cumin; season with salt and pepper. Cook, stirring occasionally, until softened, about 7 minutes. Return sliced chicken to skillet and toss until combined. Serve with tortillas and top with a squeeze of fresh lime juice.