Streusel: In a medium bowl, mix together flour, brown sugar, oats and cinnamon. Cut in butter until crumbly with pastry cutter or two knives/forks (this will take a at least 5 minutes). Stir in pecans. Refrigerate until ready to use.
Blondie Base: Spray a 9x13 baking dish with nonstick baking spray or to easily remove blondies, line baking dish with overhanging foil or parchment paper and spray with nonstick spray. Set aside.
Whisk flour, baking powder and salt together in medium bowl; set aside. Whisk sugar and melted butter in a separate medium bowl until combined. Mix in eggs and vanilla until well combined. Using a rubber spatula, fold flour mixture into egg mixture just until combined. Do not overmix. Pour into prepared baking dish and bake at 350 degrees F for 10 minutes.
Apples: Meanwhile, add all of the Apple Topping ingredients to a large bowl and toss to evenly combine. Set aside.
Assemble: Remove blondies from oven after 10 minutes. Layer with a single layer of apples (I did 3 rows) and then another layer of apples on top of that until apples are gone. Evenly sprinkle Pecan Streusel over apples.
Bake: at 350 degrees F for 20-25 minutes or until blondies are cooked through and apples are tender. Let cool completely on a wire rack before removing from pan. Refrigerate if not serving immediately.
Easy Creamy Caramel: Meanwhile, prepare Easy Caramel according to directions. Add an additional 1/4 teaspoon salt plus more to taste if desired. Drizzle bars with desired amount of caramel OR top individual bars with vanilla ice cream (optional but highly recommended) and drizzle with desired amount of caramel.
*This recipe only requires 1/2 recipe Caramel but I recommend just making the full recipe and drizzling recipes over ice cream or eating with a spoon. Because you will want to eat it with a spoon.