How to Make It
Make the crust In a food processor, pulse the 1 1/2 cups of flour with the granulated sugar and salt. Add the butter and pulse until the mixture resembles coarse meal, with some pea-size pieces of butter remaining. Sprinkle the ice water on top and pulse until evenly moistened. Turn the dough out onto a work surface, gather up the crumbs and form into a ball. Flatten into a disk, wrap in plastic and refrigerate until firm, about 1 hour.
On a lightly floured work surface, roll out the dough 1/8 inch thick. Ease the dough into a 9-inch deep-dish glass pie plate. Trim the overhanging dough to 1/2 inch, fold it under itself and crimp decoratively. Refrigerate the crust until chilled, about 15 minutes.
Meanwhile, make the streusel topping In a medium bowl, combine the flour, oats and brown sugar. Using your fingertips, blend in the butter until clumps form. Refrigerate until ready to use.
Make the filling Preheat the oven to 375°. In a large bowl, toss the apples with the flour, cinnamon and salt until evenly coated.
In a large skillet, combine both sugars and cook over low heat, swirling the pan occasionally, until the sugar is melted and the caramel is amber in color, about 5 minutes. Add the cream, butter and lemon juice (the caramel will bubble vigorously) and cook, stirring occasionally, until smooth, about 5 minutes.
Mound the apples in the crust. Pour the caramel over the apples and bake for about 30 minutes, until the crust is lightly golden. Top the apples with the streusel and bake for about 40 minutes longer, until the apples are tender and the topping is golden. Transfer to a rack to cool completely. Serve with whipped cream.