In a 2-quart microwave-safe dish with lid, stir together onion, apple, garlic, ketchup, and curry powder. Add 1/4 cup water. Season with salt and pepper; stir to combine.
Add chicken; season with salt and pepper. Cover and microwave on high for 5 minutes. Turn chicken pieces over. Cover and microwave on high for 5 minutes longer or until chicken is opaque throughout. Lift chicken from dish, and divide among four serving plates.
Stir yogurt into onion-apple mixture in dish; spoon sauce over chicken, and sprinkle cilantro over each plate. Serve with rice or noodles, if desired.