Summer squash and zucchini have a mild flavor but allowing it to brown develops more depth. I like to cut it in large slices and grill it so it's thick and meaty, like a steak. Summer squashes and mint go really well together and here, the acid from the tomatoes pulls it all together.
4 medium or 2 large zucchini or yellow summer squash
2 to 3 tablespoons olive oil, plus extra for brushing the squash
1-pint yellow cherry tomatoes, such as Sunrise Bumblebee, halved, or 2 to 3 medium tomatoes, cut into ½-inch chunks
2 green onions, sliced
1 medium garlic clove
1 to 2 teaspoons red wine vinegar
Mint, a few sprigs
1/2 cup hazelnuts, roasted and roughly chopped
To cook the Squash:
Heat a barbecue grill to medium-hot, or heat a stovetop grill pan or cast-iron skillet over medium-high heat.
Slice the zucchini lengthwise in large slices about 1/2-inch thick. Season them with salt and brush with olive oil. In batches, grill them for 3 to 4 minutes per side, until lightly browned and tender. Transfer to a plate.
To make the sauce:
In a large bowl, stir together the tomatoes and green onions. Grate in the garlic with a microplane and stir in 2 to 3 tablespoons olive oil, 1 teaspoon vinegar, and salt to taste. Let it stand about 10 minutes until juicy, then taste, adding more of what you wish.
Pile up the grilled squash on plates. Spoon the sauce on top and garnish with torn mint leaves and chopped hazelnuts.