In large bowl, toss apples with lemon juice. Add sugar, flour and cinnamon; toss to combine. Scrape into pie shell. Sprinkle with topping.
Bake in bottom third of 425 F (220 C) oven for 15 minutes.
Reduce heat to 350 F (180 C); bake for about 80 minutes or until filling is bubbly and thickened. Let
cool on rack. (Make-ahead: Set aside for up to 24 hours.)