Blend flour and salt together in a large bowl. Cut in the butter using a pastry blender (or pulse in a food processor) just until most of mixture resembles coarse meal. Mix the vinegar and 5 tablespoons of ice water together and drizzle evenly over the flour mixture and gently stir with a fork. You may need a little more water but just enough so the mix holds together when a handful is squeezed.

Pour the mixture onto a lightly floured surface, it will look crumbly but it will all come together. Using a pastry scraper, scrape the dough together and press it into a ball, and then flatten into a disk. Chill dough, wrapped in plastic wrap, until firm, at least 30 minutes.

Roll out dough on a floured surface using a rolling pin into a 15-inch circle,. Fit the pastry into a 11″ tart pan, lifting and gently pressing against the sides. Trim any excess pastry and crimp if desired. Lightly prick bottom with a fork and chill until firm, about 30 minutes. I just put it into the freezer for 10-15 minutes. (If using a tart pan with a revomable bottom place the pan on a baking sheet when putting it into the oven).

Preheat oven to 375°F.

Spray a large piece of aluminum foil with non-stick oil and fit it, sprayed side down, into the pastry shell, pressing firmly. Add pie weights.and bake 15 to 20 minutes. Carefully remove foil and weights and bake shell until golden, 10 to 15 minutes more. Transfer baked shell to a rack to cool.

Melt the butter in a large skillet over medium heat and cook the onions, stirring frequently, until they begin to caramelize and turn golden brown. Distribute the onions evenly over the bottom of the cooked, cooled crust then sprinkle them with the thyme leaves.

In a bowl, add the shredded cheese and toss with the flour. Sprinkle the mixture evenly over the onions and thyme.

In a separate bowl, beat the eggs and cream together with the salt and pepper. Pour the mixture over the quiche and top with the crumbled crisp bacon.

Place the prepared dish on a baking sheet and transfer to the middle of the oven and bake at 400°F for 15 minutes then reduce the heat to 325°F and continue to bake for an additional 25-30 minutes, until the top is lightly browned and a knife inserted into the center comes out clean.

Remove from the oven and allow to cool for five (5) minutes before serving.