I recently rummaged up this recipe from a long time ago. I used to make it all the time when I had my personal chef business. I often used it for an appetizer when serving a large group. 
 
My husband and I ate it for dinner the other night, and I forgot how delicious it is. I believe he ate the leftovers for breakfast and lunch the following couple of days. I rarely eat gluten, so I had to be good and leave the leftovers for him. He was quite happy with that. 
 
Yield 8 - 10 servings
 
2 cups flour
1½ tsp salt
12 Tbsps butter (1½ sticks), cut into chunks
7 Tbsp ice water
1½ large yellow onions, sliced thin
2 Tbsp olive oil
½ lb. Jarlsberg cheese, grated
1 zucchini, sliced thin into rounds
⅓ cup kalamata olives, sliced into thirds
Salt and pepper
 
In a food processor, mix the flour, salt, and butter and blend until the mixture has pea-sized butter pieces. Add the ice water 3 Tbsps at a time while pulsing the dough. You know the dough is done when you can take some of the mixture, squeeze it, and it sticks together. 
 
Place the dough on to a clean work surface and smear the dough in 3 or 4 motions with the heel of your hand. Form the dough into a disk. Wrap it with plastic wrap and refrigerate for at least one hour 
 
In a large skillet on medium heat, add the onions and olive oil. Cook the onions until they are softened and become caramelized. Do not over stir the onions to assure they become golden brown color. Cool the onions.
 
Preheat oven to 375℉
 
On a lightly floured surface roll the dough into a 12-inch round. Carefully fold the dough in half and place it in a 10-inch tart pan with a removable fluted rim. Unfold the dough and press it to the sides of the pan and trim the edges. Spread the onion mixture on to the dough and top with the cheese. Arrange the zucchini rounds in concentric circles over the cheese. Sprinkle the olives over the top and season lightly with salt and pepper.
 
Bake the tart for one hour or until the crust is golden. Cool the tart on a rack. Remove the rim from the pan and serve in slices at room temperature. 
 
Just Salt It, and enjoy!