Cayenne-Rubbed Chicken w/Avocado Salsa

Coarse salt and ground pepper
1/4 tsp cayenne pepper
4 boneless, skinless chicken breast halves, (6 to 8 ounces each)
2 Tbsp olive oil
1 medium red onion, finely diced
2Tbsp fresh lime juice
1 Hass avocado, pitted and cut into chunks

In a small bowl, combine 1 teaspoon salt, 1/4 teaspoon pepper, and cayenne; rub all over chicken. In a large skillet, heat oil over medium. Add chicken, and cook until browned on the outside and opaque throughout, 8 to 10 minutes per side. Meanwhile, in a medium bowl, combine onion and lime juice; set aside. Just before serving, fold avocado chunks into onion mixture; season with salt and pepper. Serve chicken topped with salsa.