This is a summer greatest hit. Grilling herbs is so underrated, and here the scallions and chives collaborate to provide a charred onion flavor that is great against the sweetness of the tomatoes. Use bigger or small tomatoes if you like and adjust the grill time accordingly. You just want to give everything a slight char and serve warm over the creamy ricotta. The lime is so good with the chives, and the balsamic is tasty with the tomatoes. Make the dressing in advance, then grill and serve. You can also make the dish entirely in advance, and serve chilled.