Preparation / Directions:
1. Drain the tofu, arrange it in a single layer on a baking sheet or tray lined with paper towels. Cover with another baking sheet and weight with heavy objects. Let stand for 1 or 2 hours. 2. Combine all the marinade ingredients in a non-reactive bowl and blend well. 3. Cut each slab of tofu into 4 rectangles and arrange them in a shallow non-reactive container. Pour marinade over the tofu and, cover and refrigerate for 24 hours. Return to room temperature before grilling. 4. An hour before cooking, place sesame seeds in a small skillet over medium heat and toast until fragrant, about 5 minutes. Cool on a plate. 5. Prepare an open grill for moderate direct heat. Soak 8 bamboo skewers for about 20 minutes. 6. Remove tofu, reserving the marinade. Beginning with the root end, thread the onion pieces lengthwise on skewers alternating with the tofu. Order the onion pieces to look like a whole onion. 7. When the grill is ready, lightly brush the rack with oil. Place tofu on the rack and cook, turning to grill each side and brushing frequently with the marinade until lightly browned on all sides. 8. Sprinkle the tofu with reserved sesame seeds and serve immediately.