3 medium onions, halved pole to pole, and sliced 1/4-inch thick.
2 teaspoons olive oil
1 teaspoon kosher salt
1 Pillsbury refrigerated pie crust, room temperature
4 slices deli Swiss cheese

1. Heat a 12-inch, non-stick skillet over medium-high heat for 2 minutes. Add the olive oil and let it heat for 10 seconds. Add the onions and salt, and cook, stirring occasionally, until you start to get some nice color, about 5 minutes.

2. Once you've started to get some nice color and char marks, turn the heat down to medium. And let it cook. And then stir. And let it cook. And then stir. And let it cook. You get the idea. This doesn't go fast--it will take 45 minutes or so--but it's so worth it.
3. While the onions are cooking, prepare the tart shells: Heat your oven to 425. Unroll the pie crust and cut it into 4 wedges. Carefully lay a pie-crust wedge in a 3-inch non-stick tartlette pan; use your knuckles and fingertips to press the pie crust to the sides and bottom of the pan. Press the overlap against the top edge of the pan to trim the excess. (Don't worry about the extra dough; we won't waste it. Read all the way down to the end of the post...) Prick the bottom several times with a fork. Bake the tart shells for 6-8 minutes, or until lightly browned.
4. Cut each slice of cheese into 4 triangles, and lay 3 or 4 pieces on each shell. Divide the onions between each shell. Return the tarts to the oven, and bake them until the cheese is melted and the shell is golden brown, 8-10 minutes.
Makes 4 tarts
Here's something yummy to do with the excess dough: Line a baking sheet with parchment paper or aluminum foil. Lay the pie crust pieces on the prepared baking sheet, brush them with melted butter, sprinkle them liberally with cinnamon-sugar, and bake them in your already pre-heated 425 deg. oven for 5-7 minutes, or until they're just starting to brown. If you really wanted to go over-the-top, you can mix 1 cup powdered sugar, 1 tablespoon of your left-over melted butter, a couple drops vanilla, and enough milk to make the icing drizzle-able. Then you can drizzle the icing over everything (like dessert nachos), or you can dip them in the icing (like dessert chips-and-dip). Waste not, want not! :)