1. Preheat grill to high. Place a 12-inch cedar plank on grill. Cover with lid to heat evenly.
2. In a bowl, combine tomatoes, ginger, garlic, and onion. Mix well.
3. Slit tilapia lengthwise and fill it with the tomato mixture.
4. Flip over the plank, and lay bok choy on it.
5. Place fish on bok choy. Sprinkle salt and pepper. Cover with lid, and cook until done.
6. Remove fish from grill, and place it on a plate.
7. Sprinkle lemon juice on top, and serve fish with sauteed shrimp and a bread of your choice.