Prep the chicken: In a bowl, toss chicken pieces with 1 tablespoon cornstarch, 1 tablespoon soy sauce, 1 tablespoon orange juice, garlic powder, pepper, and salt. Let it sit while you make the sauce components, 10 minutes.
Make the sauce base: In a small bowl or measuring cup, whisk orange juice, orange zest, soy sauce, rice vinegar, honey, tomato paste, garlic, ginger, and red pepper flakes.
In a separate cup, mix 2 teaspoons cornstarch with 2 tablespoons cold water to form a slurry. Set both aside.
Sear the chicken: Heat oil in a large nonstick skillet over medium-high. Add chicken in an even layer.
Cook 4–6 minutes, stirring once or twice, until lightly browned and cooked through. Do not overcrowd; work in two batches if needed.
Simmer with sauce: Reduce heat to medium. Pour the orange sauce base into the skillet.
Stir and let it bubble for 1–2 minutes.
Thicken the sauce: Give the cornstarch slurry a quick stir, then drizzle it into the pan while stirring. Cook another 1–2 minutes until the sauce turns glossy and clings to the chicken. If it gets too thick, splash in a tablespoon of water.
Taste and adjust salt, vinegar, or honey as needed.
Cook the sides: While the sauce thickens, steam broccoli and reheat or cook rice. For extra flavor with minimal fat, squeeze a little lemon over the broccoli and add a pinch of salt.
Assemble meal prep bowls: Divide rice and veggies among 4 containers. Top with orange chicken and spoon any extra sauce over the rice.
Garnish with green onions and sesame seeds if you like.