Preheat oven to 375 degrees. Toss the cut apples with lemon juice, sugar, flour, cinnamon, and salt. Pour into an unbaked pie shell and bake for 20 minutes. Meanwhile, melt the butterscotch chips with the butter in a double boiler or in the microwave. Remove from heat and stir in the flour and salt. Crumble this mixture over the pie and bake for an additional 20-25 minutes, until nicely browned on top and the apple mixture bubbles. Cool the pie for about 1 hour before slicing.