Preheat the oven to 400 degrees F. Line a pie plate with a pie crust.
Sift the 2 tablespoons of flour, 3/4 cup of sugar, and salt together in a medium bowl.
Combine the sour cream, egg, and vanilla and add to the dry ingredients. Beat until smooth.
Add the apples and mix well. Pour the mixture into the prepared pie plate.
Place in the preheated oven and bake for 15 minutes, then turn the temperature down to 350 and continue to bake another 30 minutes
Prepare the topping for the pie, while it is baking. Combine the 1/3 cup of sugar, 1/3 cup of flour, cinnamon. Add the butter and mix until well combined.
When the pie has been baked remove from the oven. Turn the temperature back up to 400 degrees F.
Sprinkle the topping over the pie and return to the oven and for an additional 10 minutes. Remove and cool on a cooling rack.