Step 1

Preheat oven to 350 degrees F. Coat a 9- x 13-inch baking dish with cooking spray.

Step 2

In a large bowl, beat butter and 1/3 cup sugar until creamy. Beat in sour cream, egg, and salt. Stir in flour until a soft dough forms. Spoon half the dough into bottom of baking dish and gently press down.

Step 3

In a large bowl, combine apples, remaining 1/2 cup sugar, and 1 teaspoon cinnamon; mix until apples are evenly coated. Distribute apples evenly over dough, then cover with remaining dough.

Step 4

In a small bowl, combine topping ingredients. Sprinkle over dough.

Step 5

Bake 40 to 45 minutes, or until golden brown. Let cool completely, then cut into bars.