1. Pour 2 cups water into a medium pot. Chop 1 tomato and add to pot. Add lemon, celery, onions, and ginger, and bring to a boil over high heat. Reduce heat to medium and simmer for 20 minutes. Add pineapple juice, vinegar, tomato sauce, and sugar. Mix well, then simmer for 30 minutes more.

2. Meanwhile, season pork with salt, pepper, and garlic powder and set aside for 20 minutes. In a small bowl, mix together flour, 4 tbsp. cornstarch, and enough water (about 1/2 cup) to make a smooth batter. Pour oil into a skillet to a depth of 1 1/2" and heat over medium-high heat until hot, about 350°. Dip pork in batter, shake off excess, then fry in batches until crisp and golden, about 4 minutes per batch. Drain on paper towels.

3. Quarter remaining 2 tomatoes and set aside. Combine remaining 1 tbsp. cornstarch with 2 tbsp. water in a small bowl and mix well. Add cornstarch mixture to sauce, increase heat to medium-high, and simmer for about 2 minutes. Add pineapple to sauce, cook for 30 seconds, then add quartered tomatoes and pork. Heat through, then serve with white rice, if you like.