Preheat the oven to 350°F. Grease a 9x13-inch baking pan with nonstick spray and set aside.
Using a hand mixer, beat the butter, sugars, and oil together.
1 cup unsalted butter, ¾ cup granulated sugar, ¾ cup brown sugar, ¼ cup vegetable oil
Beat in the vanilla, eggs, and sour cream.
2 teaspoons pure vanilla extract, 3 large eggs, ½ cup sour cream
In a separate bowl, whisk the all-purpose flour, baking powder, cinnamon, and salt together.
3 cups all-purpose flour, 2 teaspoons baking powder, 1 teaspoon ground cinnamon, ½ teaspoon kosher salt
Add the dry ingredients to the wet ingredients and mix until just combined.
Fold in the apple pieces.
2 medium apples
Transfer the batter to the prepared baking pan.
Combine the streusel topping ingredients (butter, flour, brown sugar, cinnamon, and salt) until the mixture is crumbly. Then, sprinkle the crumbs over the batter.
½ cup unsalted butter, 1 cup all-purpose flour, ¾ cup brown sugar, 1 teaspoon ground cinnamon, ⅛ teaspoon kosher salt
Bake for 40-45 minutes or until a toothpick inserted comes out clean.
Whisk together the powdered sugar and 2 tablespoons of milk to create a runny glaze.
1 cup powdered sugar, 2 tablespoons milk
Drizzle the glaze over the cake.