To make the crust: In the food processor, pulse the flour, butter, cheese, and salt until the butter and cheese are in small pieces coated with flour, about 15 times. Add the ice water all at once and process until the mixture almost forms a ball. Form the dough into a 6- by 4-inch rectangle using plastic wrap and a bench scraper to firmly press the dough into a cohesive form. Wrap tightly and refrigerate a minimum of 4 hours.
Remove the dough from the refrigerator and allow it to warm slightly. Divide the dough into two pieces, one slightly larger than the other. Roll out the larger piece to 11 by 15 inches and place in the slab pie pan, pressing it into the corners of the pan and allowing the excess to drape over the sides. Refrigerate. Roll out the second piece of dough to 10 by 14 inches, place it on a lightly floured sheet of parchment, and refrigerate.
Heat the oven to 425 degrees; if you have one, place a baking stone, Baking Steel, or inverted baking sheet on the center rack to heat.
To make the filling: In a large bowl, mix together the granulated sugar, maple sugar, flour, cinnamon, and salt. Add the lemon juice and sliced apples and stir gently. I like to use my hands for this. Scrape the filling into the crust in the slab pie pan and top with the dots of butter. Place the top crust over the filling, trim, crimp, and slash.
With a pastry brush, paint the water across the surface of the pie, avoiding the edges. Sprinkle the maple sugar across the top of the pie. Bake (on top of the steel, stone, or baking sheet if usinfor 20 minutes. Reduce the heat to 350 degrees and bake an additional 40 to 45 minutes. If the top gets too dark, tent with foil. The pie is done when the filling is burbling through the slashes.
Cool the pie thoroughly before serving. But if a warm pie is your heart’s content, slip the cooled pie in a hot 350-degree oven for 10 minutes before slicing.