28 ounces extra-firm tofu 5 cups barbecue sauce, like a double batch of Pomegranate-Peach Barbecue Sauce 4 ounces small round potatoes, halved 3 tablespoons extra-virgin olive oil, plus more for oiling 1 tablespoon freshly squeezed lemon juice 1 large clove garlic, minced 1 teaspoon coarse sea salt Pinch of cayenne pepper 1 medium globe eggplant (about 1 pound), cut into 1-inch chunks 1 medium green bell pepper, cut into 1-inch squares 1 large red bell pepper, cut into 1-inch squares 1 large red onion, cut into four pieces vertically, then halved crosswise