Prepare the yogurt marinade. Mix all the ingredients except for the chicken, potatoes, and red onion in a small bowl. Taste for level of spice (heat) you prefer. In my opinion, 2 tablespoons of chili garlic sauce is a little spicy. Four tablespoons is very spicy. Place the chicken into a plastic ziplock bag. Add the yogurt marinade and seal the bag. Move the chicken around until all the pieces are fully coated. Marinate in the refrigerator at least 6 hours. Overnight is preferred for optimal flavor and juiciness.
When ready to bake, place the marinated chicken onto a rimmed sheet pan. Make sure the sheet pan is rimmed or you'll have juices dripping all over the bottom of your oven! Placed the potatoes and onions around the chicken. Sprinkle everything with fresh cracked pepper. Optional: sprinkle with chili powder as well.
Place into a preheated 425 oven and set the timer for 20 minutes. After 20 minutes, stir the potatoes and return the pan to the over. Bake for an additional 20 minutes or until the chicken is fully cooked and no longer pink. Garnish with fresh cilantro.