Prepare the chicken: Cut the boneless chicken thighs into 2 inch bite-sized cubes and place them in a bowl.
Marinate the chicken: Season with salt, black pepper, garlic powder, sesame oil, and cornstarch. Mix well to coat each piece evenly. Let it sit for 10–15 minutes or as long as your schedule allows.
Pan-sear the chicken: Heat a little oil in a pan over medium-high heat. Add the marinated chicken and sear until golden brown on each side, about 2 minutes. Then cover with lid and cook for 3 minutes.
Add the lemon flavor: Once the chicken is cooked, drizzle in fresh lemon juice and diced green onions. Toss well to coat and let it cook for another 30 seconds to soak up the flavor.
Serve and enjoy: Spoon the lemon pepper chicken over a hot bowl of rice, serve with vegetables. Optional, top with an onsen egg. Enjoy!