Step 1 In a small bowl, add the salt to the water and stir to dissolve. Keep very cold until ready to use.
Step 2 To make the dough in a food processor, put the flour in the work bowl. Cut the butter into 1-inch pieces and scatter the pieces over the flour. Pulse briefly until the mixture forms large crumbs and some of the butter is still in pieces the size of peas. Add the water-salt mixture and pulse for several seconds until the dough begins to come together in a ball but is not completely smooth. You should still be able to see some butter chunks.
Step 3To make the dough by hand, put the flour in a mixing bowl. Cut the butter into 1-inch pieces and scatter the pieces over the flour. Using a pastry blender, cut the butter into the flour until the mixture forms large crumbs and some of the butter is still in pieces the size of peas. Drizzle in the water-salt mixture and toss with a fork until the dough begins to resemble a shaggy mass. Gently mix until the dough comes together into a ball but is not completely smooth. You should still be able to see some butter chunks.
Step 4On a lightly floured surface, divide the dough into 2 equal balls and shape each ball into a 1-inch-thick disk. Wrap well in plastic wrap and chill for at least 2 hours or overnight. (Meanwhile, if you haven't already, prepare the lemons.)
Step 5On a lightly floured surface, roll out one disk of dough to one-eighth-inch thick, rolling from the center toward the edge in all directions. Lift and rotate the dough a quarter turn every few strokes to discourage sticking, and work quickly to prevent the dough from becoming warm. Lightly dust the work surface with extra flour as needed to prevent sticking.
Step 6Roll the dough to make a round 1 1/2 inches larger than the pan. Carefully transfer the round to a 9-inch tart pan with a removable bottom (folding it in half or into quarters to simplify the transfer if necessary), easing it into the bottom and sides and then pressing gently into place, leaving a 1-inch overhang. Roll out the remaining disk to make a second round for the top crust. Cover and refrigerate.