1 1/4 cups all-purpose flour
1 cup light-brown sugar
1/2 cup granulated sugar
1/2 teaspoon cinnamon
12 tablespoons (1 1/2 sticks) unsalted butter, cold
To make the topping, with an electric mixer on low speed, blend the four, the sugars and cinnamon. Cut the butter into 12 pieces, and add it while mixing. Stop the mixer once the mixture starts to clump.
Preheat oven to 350 degrees. Toss the apple slices, lemon juice, flour, maple syrup and cinnamon in a bowl. Transfer the mixture to a shallow 2 1/2-quart non-aluminum baking dish. Sprinkle the topping evenly over the apples. Bake until the topping is lightly browned and the apples are tender, approximately 40 minutes.