Preheat oven to 375°F (190°C). Grease a 9-inch (23 cm) pie pan.
Press pie crust into the greased pie pan. Set aside.
In a large bowl, cream together butter and sugar until light and fluffy. Beat in eggs one at a time, then stir in vanilla.
In a separate bowl, combine flour, baking powder, and salt. Gradually stir into the creamed mixture alternately with milk.
Pour batter into prepared pie pan. In a small bowl, combine flour and sugar for the crumb topping. Stir in melted butter until mixture is crumbly. Sprinkle over the top of the cake.
Bake in preheated oven for 35 to 40 minutes, or until a toothpick inserted into the center of the cake comes out clean.
Interesting Facts
Pie-cake is a great way to use up leftover pie crusts.
You can add other ingredients to the cake batter for variation, such as chopped nuts, dried fruits, or chocolate chips.
You can also experiment with different types of pie crusts, such as graham cracker or shortbread.