Preheat the oven to 400°F. For the crust, in a 9-inch pie plate whisk together the flour, sugar and salt. Pour the oil and milk over the dry ingredients and stir with a fork until the dough is evenly moistened. Gently press the dough evenly over the bottom and up the sides of the pie plate. Press the tines of a fork into the edge of the crust to crimp.
For the filling, gently toss together the apples, sugar, flour, cinnamon, lemon juice and zest and salt. Pour into the pastry-lined pie plate.
For the topping, blend the flour, butter, brown sugar and oats together with a fork until well mixed. Evenly distribute over the top of the pie.
Bake the pie in preheated oven for 20 minutes. Reduce the heat to 350°F and bake for an additional 40 to 45 minutes or until slow bubbles form in the juices around the pie. If the crust is browning too quickly during baking, cover with a sheet of foil or a foil ring. Remove the pie from the oven and let cool at least 4 hours before slicing and serving. Drizzle the pie with half of the caramel sauce, cut into wedges and serve with remaining caramel sauce.