Preheat your oven to 350 degrees F (175 degrees C) and grease baking sheet. In a large bowl, combine the apple wedges. Sprinkle 1 teaspoon of cinnamon and the brown sugar over the apples, then toss to coat.
Add ½ cup of flour to the apples and mix thoroughly. Spread this apple mixture onto the prepared baking sheet. In another bowl, place the remaining ½ cup of flour. Using 2 knives or a pastry blender, cut in the cold butter until the mixture resembles small peas.
Add the other teaspoon of cinnamon, rolled oats, chopped walnuts, maple syrup, vanilla extract, and salt. Stir the mixture until it is well combined. Carefully spoon the oat and walnut mixture over the apples on the baking sheet, evenly distributing it.
Bake the dish in the preheated oven for approximately 45 to 50 minutes, or until the fruit mixture is bubbling, top is lightly browned and fruit is as tender as you'd like it to be.