Preheat oven to 350 degrees.
Cut chicken into bite-sized pieces and spread out in a single layer in a 9 X 13 inch pan sprayed with non-stick cooking spray (you could also use a 9x9" baking pan.)
In a medium saucepan over high heat, whisk together the sugar, soy sauce, water, onion powder, garlic, and ground ginger. Bring to a boil. Reduce heat to low and simmer 5 minutes.
Remove mixture from heat and whisk in lemon juice and red pepper flakes.
Pour mixture over chicken. Cover pan with foil and bake for about 35 minutes, stirring halfway through to make sure chicken is evenly covered with sauce.
When finished cooking, drain some of the leftover juices into a saucepan. Place saucepan over medium-high heat and heat up juices to make a sauce. If desired, add 1 teaspoon cornstarch to the juices to make a thicker sauce (completely optional, but I love when the sauce is a little thicker).
Add steamed broccoli to chicken in the pan and mix gently.
Put chicken/broccoli mixture over cooked rice and drizzle thickened sauce over the top. Sprinkle sesame seeds on top.
(This also works great with pork!!)