Cut tenderloin into 1 1/2 inch x 1 1/4 inch strips; set aside. Drain pineapple, reserving juice. Set pineapple aside.
To juice, add ketchup, water, soy sauce, vinegar, brown sugar, cornstarch, salt and pepper and ginger. Stir well until smooth.
Heat oil in a large skillet or wok over high heat.
Stir fry pork and onion for 5-7 minutes or until pork is no longer pink. Stir pineapple juice mixture and add onion, pepper strips and pineapple tidbits to skillet and cook, stirring until thickened and bubbly. Reduce heat, cover and cook for another 5 minutes. Serve immediately over hot cooked rice. Makes 4 servings. Enjoy!