01 - Preheat oven to 350°F. Lightly grease a baking dish sufficient to arrange apples in a single layer.
02 - Brush apples with lemon juice and place cut side up in the prepared dish.
03 - Combine brown sugar, cinnamon, and nutmeg in a small bowl; sprinkle evenly over apples.
04 - Mix oats, flour, brown sugar, cinnamon, and salt in a medium bowl. Cut in cold butter with fingertips until mixture forms coarse crumbs.
05 - Evenly distribute oat crumble over apples, gently pressing to adhere.
06 - Bake for 30 minutes or until apples are tender and topping is golden brown.
07 - Serve warm, optionally accompanied by vanilla ice cream or Greek yogurt.