Step 1: In a medium-sized pan or small saucepan, combine all the ingredients: onion powder, garlic powder, black pepper, salt, cayenne powder, red pepper flakes, sugar, soy sauce, water, and cornstarch.

Step 2: Turn the heat to medium and whisk the ingredients together until the cornstarch has dissolved completely. This will help prevent any lumps from forming.

Step 3: Allow the mixture to simmer on medium heat. Stir continuously to avoid burning the sauce at the bottom of the pan. As the sauce heats up, the cornstarch will begin to thicken the mixture.

Step 4: Continue cooking and stirring for about 5-7 minutes, or until the sauce reaches your desired consistency. The sauce should be thick enough to coat the back of a spoon.

Step 5: Once thickened, remove the pan from heat and allow the sauce to cool slightly before transferring it to a jar or container.

Step 6: Pour the sauce into a clean jar or airtight container, then seal and store it in the refrigerator. The sauce will keep for up to 3 days in the fridge.