Preheat oven to 350°F (175°C). Lightly butter a 9x9-inch square or 10-inch round deep ceramic baking dish.

In a large mixing bowl, combine sliced apples, whole cranberries, granulated sugar, pure maple syrup, cornstarch, fresh lemon juice, ground cinnamon, and nutmeg. Toss gently until every fruit slice is evenly coated and glossy.

Transfer fruit mixture into prepared baking dish and spread into an even, level layer.

In a separate medium bowl, whisk together rolled oats, flour, dark brown sugar, chopped pecans, cinnamon, and fine salt.

Pour melted butter over dry oat mixture and stir with a fork until moist, clumpy, uneven clusters form.

Scatter clumpy oat streusel evenly over apple cranberry layer, covering fruit generously edge-to-edge.

Bake at 350°F (175°C) for 42 to 48 minutes, until cranberry juices are bubbling vigorously along edges and oat topping is deep golden brown and fragrant.

Remove from oven and let rest on a wire rack for 15 minutes before serving so fruit juices thicken into a luscious saucy glaze. Serve warm with scoops of vanilla bean ice cream.