This is a tasty recipe I got from an old church cookbook; I have changed a few minor things about it. Cooking the pie in a brown paper bag allows for nice, even browning with no burnt edges. It bakes perfectly every time.
1 unbaked piecrust
5-7 Granny Smith apples, or other tart baking variety, peeled and sliced
2 T lemon juice
1/4 c sugar
1 tsp cinnamon
1/4 tsp nutmeg
2 T flour
3/4 c sugar
3/4 c flour
3/4 c butter (1 1/2 sticks), softened
Combine apple slices (thin) with filling ingredients in a large bowl. Transfer to pie shell. Then, you can use the same bowl to combine the 3 topping ingredients; mix with a fork until it's the consistency of cookie dough. Pat the topping evenly over the apples; going all the way to the edges.
Open a heavy brown paper bag (grocery bag) and lay it on its side onto a large baking sheet. Slide pie into the bag, fold the end and secure with paper clips. Bake at 425 for 1 hour.