Add flour, sugar, and salt into a bowl. Give a stir.
Add egg, vanilla, sour cream and nutmeg. Stir until smooth.
Stir in diced apples.
Pour into greased 8x8 baking dish.
Bake at 350 degrees for 30 minutes.
While baking, mix topping ingredients to a crumb consistency.
At 30 minutes sprinkle topping over the top and bake 10-15 minutes more.
Allow to cool 30 minutes before serving.
You can also garnish with whip topping, ice cream and or carmel syrup.