1) Preheat the oven to 425°F.
2) To make the crust: In a medium-size mixing bowl, whisk together the flour and salt.
3) Using an electric mixer, a pastry blender or fork, or your fingers, cut and mix the cheese and butter into the flour mixture until the fat and flour form a crumbly mixture.
4) Add the lemon juice or vinegar, then sprinkle on just enough water so that you can gather the dough into a cohesive ball.
5) Divide the dough in half, and flatten each half into a 1" thick round. Wrap one of the rounds in plastic wrap or waxed paper, and refrigerate it while you work with the other. Transfer the remaining dough to a well-floured work surface.
6) Roll it into a 12" circle, using as few strokes of the rolling pin as possible; the fewer times you touch the crust at this point, the more tender it'll be when it's baked. Transfer the circle of dough to a 9" pie plate (a giant spatula works great here), and gently fit it to the pan's contours. Again, if you push and stretch the dough too much during this stage, it'll shrink when you put it in the oven.
7) To make the filling: In a large, shallow frying pan, cook the sliced apples with the salt, cider or juice, and sugar for 15 minutes, or until the apples are tender and the liquid is syrupy.
8) Stir the cooked sausage into the apple mixture, and remove the pan from the heat. Spoon the filling into the crust.
9) Roll out the remaining crust, and center it over the filling. Press the edges of the top and bottom crust together, fold them under (onto the top of the pan's rim), and crimp.
10) Bake the pie for 15 minutes, then lower the oven heat to 375°F and bake for an additional 35 to 45 minutes, until the crust is very brown. If the crust appears to be browning too quickly, tent it lightly with foil.
11) Remove the pie from the oven, and serve it warm or at room temperature.
Yield: 8 to 10 servings.