2 red onions, cut into 1/2-inch rounds

12 scallions, trimmed and cleaned

1 pound snow peas or sugar snap peas, trimmed, strings removed

Kosher salt

Start with the vinaigrette. In a small bowl, whisk together the vinegar, thyme, mustard seeds and red pepper flakes.

Halve the tomatoes crosswise and gently but firmly squeeze out the seeds and juices into the bowl with the vinegar mixture -- be sure to get most, if not all, of them. Use the tomato flesh for a sandwich.

Whisk together, then continue whisking while you drizzle in the oil to form a viscous emulsion. Season with salt and pepper.

For the vegetables, preheat a gas grill or prepare a fire in a charcoal grill. Place the vegetables on three large baking sheets, keeping the snow peas separate from the others. Brush all the vegetables lightly with some of the marinade and season lightly with salt.

Place all the vegetables except for the snow peas on the grill over medium-high heat and cook for 7 to 9 minutes, until just lightly charred, and then turn and cook for 3 to 5 minutes more. Remove each vegetable from the grill as it is done and return to the baking sheets.

Place a baking sheet with the snow peas on the grill and cook 2 minutes.

To serve, arrange the vegetables on a large serving platter and drizzle with the remaining marinade. Serve warm or at room temperature.

(Mario Batali is the chef behind 25 restaurants, including Eataly, Del Posto and his flagship Greenwich Village enoteca, Babbo.)