Preheat oven to 450°F (230°C).
In a medium bowl combine flour, oats, granulated sugar, brown sugar, pecans, cinnamon, and salt.
Add melted butter and stir until mixture is fully combined and thoroughly moistened. Set aside.
To make the filling: In a large bowl toss apple wedges and sugar (or maple syrup) together. Set aside.
Set a 9-inch cast iron skillet over medium heat, pour in the apple cider and bring it to a simmer. Cook until reduced by half, about 5 minutes. Transfer cider to a small bowl, stir in the lemon juice and set aside.
In the now-empty skillet heat 1 tbsp butter over medium heat. When the foaming begins to stop, add apple mixture and cook, stirring frequently until apples begin to soften and become translucent about 12 to 14 minutes. The apples should not fully be cooked! Remove pan from heat and gently stir in cider mixture until apples are coated.
Sprinkle topping evenly over the apples.
Transfer skillet to a baking sheet in the middle position of the oven and bake until apples are tender and the topping is deep golden brown, about 15 to 20 minutes.
Transfer to a wire rack and let cool for at least 15 minutes before serving.