Add orange juice, white and brown sugar, rice vinegar, soy sauce, ginger, garlic, and red chili flakes in a medium saucepan. Stir and cook over medium heat for 3 minutes.

In a small bowl, whisk one tablespoon of cornstarch with two tablespoons of water to form a slurry. The cornstarch should be fully dissolved.

Add the slurry to the orange sauce and whisk together. Cook for 5 minutes until the mixture begins to thicken.

Once the sauce has thickened, remove from heat and stir in orange zest.