4 boneless, skinless chicken breasts ¼ cup diced onion ½ cup low sodium soy sauce ½ cup honey ¼ cup tomato paste 2 tablespoons grated ginger 1 tablespoon apple cider vinegar 2 garlic cloves, chopped 1 teaspoon sesame oil ½ teaspoon red pepper flakes 1 tablespoon cornstarch ¼ cup cold water 3 cups chopped broccoli florets hot cooked rice sesame seeds and green onions for garnish