This is a classic combination for a quiche, but it’s lighter, with a whole-wheat and olive oil crust. If you don't have the time to make the crust, store bought will work just fine.
03Heat the olive oil over medium heat in a large, heavy skillet and add the onion. Cook, stirring often, until it is tender and beginning to color, about 8 minutes. Add the spinach, thyme and salt and pepper to taste, and stir together. Remove from the heat.
04Whisk the eggs in a large bowl. Add salt to taste (I use about 1/2 teaspoon) and whisk in the milk. Stir in the onion and spinach mixture and the cheeses. Scrape into the pastry-lined tart pan. Place in the oven and bake 40 to 45 minutes, until tart is set and beginning to color on the top. Remove from the heat and allow to cool for at least 15 minutes before cutting. Serve warm or room temperature.