- Whisk onion, soy sauce, brown sugar, garlic, sesame oil, sesame seeds, and cayenne pepper together in a bowl until marinade is smooth.
- Mix chicken into marinade and cook in a large skillet over medium-high heat.
- After about 5 minutes, add the sliced zucchini to the skillet.
- Cook until the chicken is cooked through, 5-10 minutes more.
- Serve on rice.