Place apples in a pie pan and dust with cinnamon and nutmeg. Cover with foil and bake for 20 minutes.
In a food processor chop nuts with a few short pulses. Pour in sugar and flour and process to combine. Add butter and salt and process until mixture resembles coarse meal. Sprinkle topping over apples.
Bake in preheated oven for 30 minutes, or until golden brown.