Preheat oven to 350.
Cream butter and sugar, beat in egg and vanilla.
Combine flour, baking soda, and salt.
Stir into creamed mixture, alternate with buttermilk.
Fold in apples.
For topping combine flour, sugar, brown sugar, and cinnamon.
Cut in butter until crumbly.
Sprinkle over batter.
Bake for 55-60 minutes.
Cool in pan 10 minutes.