Preheat oven to 350° F.
In bowl, toss apples, pears, sugar, cornstarch, cinnamon, salt and lemon juice.
Place fruit mixture in bottom of 10-inch cast-iron pan or baking dish.
Sprinkle walnut crisp topping mixture over fruit.
Bake 45 minutes, or until fruit mixture is hot and bubbly and topping is golden brown.
Top with ice cream and drizzled with caramel sauce, if desired.