Drain pineapple, reserving juice; set aside. In a small bowl, combine the cornstarch, brown sugar, salt, ginger and pepper. Stir in the water, ketchup, vinegar, soy sauce and reserved juice until smooth., In a large skillet or wok, stir-fry pork and onion in oil for 4-8 minutes or until tender. Stir pineapple juice mixture; add to skillet. Bring to a boil; cook and stir for 1-2 minutes or until thickened., Add green pepper and reserved pineapple. Reduce heat; cover and cook for 5 minutes. Serve with rice and if desired, sesame seeds.