Preheat oven to 350 degrees F. Combine 2/3 cup sugar and 1 tsp cinnamon in a small bowl.
In a large bowl, mix apples with most of cinnamon and sugar mixture. Then place apples into a 13x9 inch baking dish. Sprinkle remaining cinnamon and sugar mixture over apples and gently mix to combine.
In a separate bowl, combine flour, sugar, eggs, baking powder, cinnamon and salt and mix with a fork until mixture looks like coarse crumbs. Sprinkle mixture over apples in baking dish.
Drizzle melted butter evenly over crumb mixture. Bake for 45-55 minutes or until starting to turn lightly golden brown. Remove from oven and allow to cool slightly.
Best served warm, with individual servings topped with a scoop of ice cream and caramel sauce.