Tomato Zucchini and Caramelized Onion Tarte

Here is a nice little appetizer, or a side dish instead of a veggie casserole.  Nuts add dimension to a savory tart crust, and toasting them especially brings out their deep flavor.  You could use most any tree nut you like for this crust.
2 large onions, sliced
4 cloves garlic, sliced
1 large zucchini, sliced thinly
2 Tbsp pesto
1 large ripe tomato, sliced thinly
1 cup cheddar (or other favorite) cheese, finely grated
1/2 tsp herbes de Provence

Crust:
1/4 cup whole hazelnuts
3/4 cups flour
1/2 tsp salt
1/2 stick butter, cubed
3 Tbsp ice water

Set onions to caramelize. Place onions in a large skillet with the butter and the oil over medium-high heat. Sauté for about 5 minutes as the onions start to brown a bit. Turn the heat down to medium and stir the onions. Cook them for the next 20 minutes, stirring often, and adjusting the heat to medium-low just to keep them browning, but definitely not burning. Lightly salt and pepper to taste.

Meanwhile, prepare the dough for the crust. First toast the hazelnuts in a 375F oven (I use a toaster oven) for about 3 to 5 minutes, shaking once or twice. Watch the nuts closely, being very careful not to burn them, which can happen quickly. Keep oven preheated at 375F.

Let the nuts cool and then tip them into a large food processor. Pulse them to form a fine, but dry grind, being careful not to over process to almond butter! Add the flour and salt and pulse together.

Next, add the butter and pulse together just enough to form a coarse mixture. Pulse in the water by the tablespoon-ful. Add only enough just so that the dough pulls together. Tip dough out onto a floured counter and form into a disk. Wrap with plastic wrap and refrigerate for 30 minutes.

While the dough chills, the onions should become nicely caramelized and brown.

Add the garlic for the last 5 minutes of cooking. Set them aside in a bowl. Then put the zucchini into the same skillet as the onion were cooked in, and sauté over medium-high heat to brown them up and allow them to lose some water. Do not add salt as this can make them limp, and there is plenty of flavor in this dish.

Take the dough from the refrigerator and roll out in plenty of flour to 12-inch diameter. Oil a 10-inch fluted tart pan (ideally with removable base) and lay dough down evenly into pan. Gently push sides into flutes and then roll top with a rolling pin to cleanly trim the edges.

Paint the pesto evenly on the bottom of the crust.

Top with the onions and garlic and then layer on the zucchini.

Sprinkle the cheese on top and then top with the tomatoes, evenly layered in a spiral.

Sprinkle with the herbs and bake for 30-40 minutes, rotating the tart once or twice if necessary to cook evenly.

Remove from tart pan, slice and serve as a side dish or appetizer.

Serves 4.