Combine all marinade ingredients in a large ziplock bag with the cubed chicken, securing and mixing well.

Refrigerate the chicken to marinate for at least 4 hours, or preferably 24 hours.

Remove the marinated chicken from the refrigerator and let it sit for 30 minutes to reach room temperature.

Whisk eggs in a shallow bowl and combine flour and cornstarch in another bowl or dish.

Heat about 1/4-inch of vegetable oil in a large skillet over medium heat.

Remove chicken from the marinade, discarding any excess.

Dredge chicken pieces in egg, then in the flour mixture. Fry in batches until golden brown and cooked through, about 5 minutes per batch, turning as needed. Transfer cooked chicken to a plate.

In a wok or a clean skillet, heat 2 tablespoons of vegetable oil over high heat. Add the red onion and stir-fry for one minute.

Add the halved tomatoes and cook for another minute. Then, stir in the ketchup, chicken broth, brown sugar, oyster sauce, sesame oil, ginger, and lemon zest and juice.

Cook the sauce for a few minutes until it thickens. Add the fried chicken and stir to coat thoroughly.

Serve the coated chicken immediately over prepared Jasmine rice, garnished with sliced green onions.