Peel the zucchini and trim the ends. Using a good quality julienne peeler, cut the zucchini into long strands of spaghetti. Keep peeling into julienne strips until you have just ½-inch of zucchini remaining in the center. Discard.

Lay out the zucchini spaghetti in one even layer over doubled up paper towels. Allow the zucchini to sit and dry out for 4 hours. In a large non-stick skillet, heat 1 tablespoon of olive oil over medium heat. Sauté the zucchini strands until just heated through and coated with oil, about 2 minutes, in batches as necessary. Set aside.

In the same pan, add the remaining tablespoon of olive oil and sauté the onion and garlic until translucent, about 2 minutes. Add the mushrooms and sauté another 3 minutes. Then add the grape tomatoes for 1 minute. Season with salt and pepper to taste.

Season the zucchini with kosher salt, add the rest of the vegetables and toss lightly with tongs. Serve at room temperature.

To make this salad in advance, store the sautéed zucchini and the rest of the vegetables separately in the refrigerator. Allow to come to room temperature, season the zucchini with salt, and then toss together with the previously seasoned vegetables before serving