I firmly believe if you go into the kitchen and start chopping an onion, an idea for dinner will soon follow.
Place the onions in a heavy-bottomed pan with the butter and ½ teaspoon of salt. Put on medium heat. You want to sweat, not brown, the onions, so stir frequently. Once they really start to cook, turn the burner to low. These should cook for about 30 minutes, until they are very soft and translucent. Remove from heat. Preheat oven to 375°.
In a bowl, whisk the remaining ½ teaspoon of salt, cream, eggs, cheese and flour. Add the onions and mix in with a spoon. Pour this mixture into the crust and bake for 35–40 minutes, until the top of the tart begins to brown and the middle of the tart is just set. Serve warm.
Grease the bottom and sides of a tart pan or pie pan. Set aside. In a mixing bowl, place the sugar, flour, baking powder, salt and butter. Beat on high until the butter is mixed in and about the size of peas. With the mixer on high, add the water 1 tablespoon at a time until the dough just comes together. Place in plastic wrap and flatten into a 6-inch disk. Put it in the fridge to chill for 1 hour.
Preheat oven to 375°. Remove the dough from the fridge and roll out to about ¼-inch thickness. It should be about 11 inches in diameter. Place the dough over tart pan and press down the sides. Press the dough down over the ridged edges of the pan to remove the excess.
Poke the crust with a fork all over the bottom of the pan and bake blind for 15 minutes.