01 - Preheat oven to 350°F. Lightly grease a 9x13-inch baking dish.
02 - Combine sliced apples with lemon juice in a large mixing bowl; mix gently. Arrange apples evenly in the greased baking dish.
03 - Combine maple syrup, brown sugar, heavy cream, butter, bourbon, and salt in a medium saucepan over medium heat. Stir frequently. Let mixture come to a gentle boil and simmer for 3–4 minutes until slightly thickened. Remove from heat and stir in the vanilla extract.
04 - Pour the warm caramel sauce evenly over the apples in the baking dish.
05 - In a separate bowl, combine oats, flour, brown sugar, cinnamon, and salt. Add cold cubed butter and blend with fingertips or a pastry cutter until the mixture forms coarse crumbs. Stir in pecans, if desired.
06 - Distribute the oat topping evenly over apples and caramel.
07 - Bake uncovered for 40–45 minutes, or until the topping is golden and apples are bubbling.
08 - Allow to cool slightly. Serve warm, optionally accompanied by vanilla ice cream.