Prepare the short pastry. Wrap tightly in plastic and refrigerate for 30 minutes, or up to a day.
Heat 1 tablespoon olive oil in a large skillet over medium heat. Add the onions, sprinkle with 1/4 teaspoon of the salt, and stir. Cover, turn the heat down to low, and cook for 30 minutes, stirring from time to time, until the onions are soft and translucent. Remove the lid, turn the heat to medium-high, and cook for another 5 minutes, stirring regularly, until most of the liquids have evaporated. (This can be prepared up to a day ahead).
Remove the dough from the refrigerator and let stand at room temperature for 10 minutes before using. Preheat the oven to 350 degrees F. Grease a 10-inch ceramic quiche pan with 1 teaspoon olive oil. Working on a lightly floured surface, roll out the dough in a 12-inch circle. Transfer the dough into the pan, prick the bottom all over with a fork, and press on the sides with your fingers so the dough will adhere. Bake for 7 minutes, until lightly golden. Remove from the oven (leave the heat on) and set aside.
In a medium mixing bowl, whisk together the eggs and cream. Season with the remaining 1/4 teaspoon salt, the pepper, and the cumin. Fold in the cheese and onions, and pour into the tart shell.
Bake for 35 minutes, until the top is golden and the centre of the quiche is still slightly jiggly. Turn the oven off and leave the quiche in the closed oven for 10 minutes, until the filling is set. Serve warm, with a salad of butterhead lettuce. You can make the quiche a few hours or a day ahead and reheat it for 15 minutes in a 350 degrees F oven to revive the crispness of the crust.