Have your pie crust ready. Mix together everything EXCEPT the fruit.
Preheat your oven to 375F
Peel, core, and slice the apples. Keep them in lemony water to keep them from browning as you prepare the remaining apples.
Place sliced apples and blackberries in a large bowl with room to mix them around. Pour dry ingredients and mix well with the fruit.
Pour everything into your prepared pie crust. Top with the rest of the crust, crimping the edge to avoid leaks. Score the top to allow the steam to escape. Use a pie shield or put strips of foil around the edge to keep it from browning too quickly.
Place a sheet of foil under the pie (to catch spills) and bake for 50 minutes at 375F Remove the pie shield (or the foil strips) and bake for another 15-20 minutes.Cool for at least 2-3 hours.