Toss 1 pound halved cherry tomatoes, 2 large, sliced peaches, the kernels cut from 2 ears of corn, 1/2 cup thinly sliced basil, 2 tablespoons extra-virgin olive oil, 2 tablespoons white balsamic vinegar, 3/4 teaspoon kosher salt, 1/4 teaspoon sumac, and a pinch of black pepper in a shallow serving bowl or platter and refrigerate until ready to use. Can prep up to 2 hours in advance, but not necessary.
When you’re ready to eat, preheat your grill or grill pan to medium-high heat. Spray 8 ounces of halloumi, sliced into 4 to 6 slices, with nonstick cooking spray, then grill for 2 to 3 minutes per side, until it has beautiful grill marks and easily releases from the grill. It will stick if it’s not ready to flip yet, but it’ll become easier once it has a nice enough sear. No grill or grill pan? Just pan sear the cheese in a nonstick skillet.
When you’re ready to serve, toss the salad again to redistribute the oil and vinegar that has settled to the bottom of the bowl. Taste, and season with more salt if needed. Add the avocado quarters and grilled halloumi on top of the salad and serve immediately.