Prepare a charcoal grill for direct grilling, high heat.
Toss the tomatoes with oil and season with salt and pepper. Transfer to a grill basket and grill until charred and slightly soft, tossing occasionally, about 5 minutes
Combine the vinegar, sugar, coriander and cumin seeds in a small saucepan and bring to a boil. Reduce the heat and simmer until thickened to a glaze, about 10 minutes. Let cool slightly, then pour over the tomatoes. Toss, mashing the tomatoes slightly. Add the herbs and the zest, toss again, taste and season.
Recipe courtesy of Bobby Flay