Heat 1 tbsp vegetable oil in the same skillet you used for the chicken over medium‑high heat.
Add 1/2 medium thinly sliced red onion to the skillet and cook for one minute. Add 1/2 cup cherry tomatoes or baby plum tomatoes or a mix, cut in half, and cook for another minute.
Add 1/2 cup ketchup, 1/4 cup chicken broth, 2 tbsp brown sugar, 2 tbsp oyster sauce, 1 tsp toasted sesame seed oil, 1/4 tsp grated ginger and 1 lemon zest and juice. Stir to combine and cook for a few minutes, or until the sauce thickens. 4-5 minutes. Reduce heat to low and keep warm.
Combine chicken pieces with the sauce. Stir to coat all the pieces and serve over white rice.