Sprinkle chicken with the remaining 1/2 teaspoon salt, the remaining 1/2 teaspoon pepper and garlic powder. Heat oil in a large skillet over medium-high heat. Add the chicken and reduce heat to medium. Cook, turning once, until just cooked through, 4 to 6 minutes per side. Top with cheese; cover and continue cooking until the cheese has melted, about 2 minutes more. Transfer the chicken to a serving platter and top with the guacamole. Garnish with cilantro.