1. Preheat oven to 350°F and grease or line a 9x13-inch baking pan.
2. Mix brown sugar, granulated sugar, cinnamon, and salt in a bowl. Stir in melted butter. Mix in flour until crumbles form. Chill.
3. Whisk flour, baking soda, baking powder, and salt. Set aside.
4. Beat softened butter and sugar on high speed until creamy. Add eggs, sour cream, and vanilla. Mix until combined.
5. Toss apples with cinnamon.
6. Spread batter in pan. Top with apples and crumb topping. Press down.
7. Bake 45-55 minutes until a toothpick comes out clean. Cover with foil if browning too fast.
8. Cool for at least 30 minutes before serving. Optional: drizzle with icing.