Preheat oven to 350°F (175°C) and butter a 9x9-inch baking dish.
Toss the sliced apples with maple syrup, brown sugar, lemon juice, cornstarch, cinnamon, and nutmeg. Spread evenly into the baking dish.
In a bowl, mix the rolled oats, flour, brown sugar, pecans, cinnamon, and salt. Cut in the cold cubed butter until coarse, pea-sized clumps form.
Scatter the streusel evenly over the apples and bake uncovered for 35-40 minutes until golden brown and bubbling.
Let cool for 10 minutes before serving warm with vanilla bean ice cream and caramel sauce.