• Preheat the oven to 350°F.

For the topping:

• Combine the butter, brown sugar, oats, flour, cinnamon, and salt and press with your fingers until thoroughly combined and clusters form. Refrigerate until needed.

For the apple filling:

• Combine 1 tablespoon of lemon juice and 1 tablespoon of water in a large mixing bowl.
• Peel, core, and slice the apples into ⅛ inch slices, tossing them in the lemon water as you add them to the mixing bowl.
• Sprinkle the apple slices with the cornstarch, brown sugar, and cinnamon. Toss until evenly coated. Put in a baking dish.

To bake:

• Remove the topping from the refrigerator, crumble into clusters, and sprinkle on top of apples.
• Bake on the middle rack for 40-50 minutes or until the fruit is bubbly the top is golden brown. Cover top with a tent of foil if the topping browns too quickly.
• It’s done when the filling is hot, bubbly, and starting to thicken. (It will thicken further as it cools.)
• Cool for about 10 minutes then serve warm with a scoop of vanilla ice cream.