Zucchini-Tomato Frittata

Preheat oven to 350 degrees (F). Position oven rack to the center of the oven.

Heat 2 tablespoons olive oil in a 12-inch stainless steel skillet over medium-high heat until hot, but not smoking. Add the zucchini and cook, stirring often, until zucchini are nicely browned, about 5 minutes. Remove pan from heat and set aside.

In a separate 12-inch nonstick ovenproof skillet, heat 1 tablespoon olive oil over medium heat. Add onion and saute until lightly browned, about 3 minutes. Add the zucchini, thyme, 1 teaspoon salt and ground black pepper. Continue to cook, stirring occasionally, for about 2 minutes more. Then remove from heat and set aside.

Meanwhile, in a large bowl, whisk together the eggs, milk and remaining 1/2 teaspoon salt until well blended. Using a fork, stir in the cheese.

Pour the egg mixture over the vegetables, gently lifting the vegetables to let the egg mixture coat the bottom of the pan. Reduce heat to medium-low heat and continue to cook, undisturbed, until sides are set , but top is slightly runny, about 10 minutes.

While the frittata is slowly cooking, arrange tomato slices on top, slightly overlapping tomato slices in a circular pattern on top of the egg mixture to cover it entirely, starting from the outer edge of pan and ending in the center of the pan. Sprinkle with a few pinches of crumbled dried thyme just to give it some color.

When frittata is finally set on the sides, transfer frittata to the preheated oven. Bake frittata until center is firm and not jiggly, about 25 minutes.

Remove frittata from the oven. Change oven temperature to broil. Reposition oven rack to the top rack and broil the the top of the frittata for about 2 to 3 minutes to slightly brown the tomato slices. Let frittata cool for about 5 to 10 minutes before serving.