Roasted Tomatoes Stuffed with Ratatouille

4 large, ripe tomatoes
Kosher salt

For the stuffing:

1 medium red onion, cut crosswise into 1/3-inch slices
1 medium red bell pepper, stem and seeds removed, cut into flat pieces
1 medium zucchini, cut lengthwise in 1/3-inch slices
Extra-virgin olive oil
Freshly ground black pepper
2/3 cup grated mozzarella cheese
1 tablespoon finely chopped fresh basil
1 teaspoon balsamic vinegar

Cut a 1/2-inch slice off the top of each tomato. Discard the tops. With a small knife cut around the inside of the fleshy part of the tomato (do not cut through the bottom of the tomato) to within 1/2 inch of the skin. With a teaspoon, scoop out the tomato flesh, leaving about 1/2 inch of flesh attached to the skin. Discard the juice and seeds to make room for the stuffing. Lightly salt the inside of the tomatoes and turn them, cut side down, on a plate lined with paper towels while you prepare the stuffing.

To make the stuffing: Lightly brush or spray the onion, pepper, and zucchini with olive oil. Season with salt and pepper to taste. Grill over Direct Medium heat until tender, turning once halfway through grilling time. The onions will take 8 to 10 minutes. The peppers and zucchini will take 6 to 8 minutes. Transfer to a cutting board and cut into 1/3-inch pieces. Combine the grilled vegetables in a medium bowl with the cheese, basil, and vinegar.

Spoon the vegetable stuffing into the tomatoes. Grill the tomatoes over Indirect Medium heat until the cheese is melted and the vegetables are warm, 8 to 12 minutes. Serve immediately.

Makes 4 servings.