Step 1

Preheat oven to 350 F. Grease a 9-inch square baking pan with nonstick cooking spray.

Step 2

In a large mixing bowl, combine apples, lemon juice, cinnamon, and sugar (if using). Gently toss to combine. Evenly distribute the apple mixture into the greased pan.

Step 3

In another mixing bowl, combine softened butter, oats, flour, sugar, and cinnamon. Stir together with a rubber spatula until combined. Evenly distribute the oat mixture on top of the apple layer.

Step 4

Bake for 40-50 minutes until the top is lightly browned and apples are bubbly. Place on a wire cooling rack to cool down for 10 minutes.

Step 5

Serve warm with whipping cream or a scoop of vanilla ice cream.