Grease and flour an 8" round or square baking pan. Set aside.
Preheat oven to 375 degrees F.
to make the topping:
In a medium bowl, whisk together sugar, salt and flour. Add melted butter and fluff with fork until mixtures creates crumbs. Set aside.
to make the cake:
In a medium mixing bowl, whisk together flour, sugar, baking powder, baking soda, salt and lemon zest. In a large measuring cup, mix together milk, vanilla, lemon extract, oil and egg. Whisk until smooth.
Add the wet ingredients to the dry ingredients and stir with a wooden spoon. Do not over mix. Few lumps in the batter are okay.
Pour the cake batter into the prepared pan.
Spoon the pie filling over the cake layer.
Sprinkle crumb topping over the filling.
Bake the cake for 30 to 35 minutes or until the topping is golden brown.
Let cool completely in the pan.
Transfer onto a serving plate or stand. Slice and serve.