Sift, flour, sugar and salt into a mixing bowl. Cut chilled butter into pieces into the bowl. Using your fingertips, rapidly rub the butter and dry ingredients together until the mixture resembles coarse meal. Be careful to use only your fingertips as your palms will warm the dough.
Stir egg yolks, vanilla and water together and add to the flour-butter mixture and blend in, using a fork. Shape dough into a ball. This should not take more than 30 to 45 seconds.
Place the ball of dough on a pastry board. With the heel of your hand, smear about ¼ cup of dough away from you into a 6- to 8- inch smear; repeat until all dough has been dealt with. Scrape dough together; re-from into a ball, wrap in wax paper, and chill for 2 to 3 hours.
Peel the pears, core them and cut into 1/4-inch slices. In a large bowl toss the pear slices with the lemon juice. Sprinkle in the cornstarch, brown sugar and cinnamon and toss until the pears are evenly coated. Set aside.
On a lightly floured surface, roll the chilled dough into a large circle about nine inches in diameter. Line a baking sheet with parchment paper, and draping the dough over the rolling pin, transfer to the prepared baking sheet. If the dough breaks at all patch it up with your fingers.
Arrange the pears in a mound in the center of the dough, leaving a 2-inch border. Fold the border over the filling. It will only cover the pears partially and does not need to be even.
Bake the tart for 15 minutes, and then reduce the oven temperature to 350 degrees F, keeping the tart in the oven all the while, and bake for another 40 minutes, until the pears are tender and the crust is golden brown.
Transfer to a plate to cool slightly. Cut into 6 wedges and serve warm or a room temperature.