Get the oven hot and ready, at 375 degrees. Prep a baking dish (8, 9, or 10 inches) with a little butter.
Add the apple slices to the serving plate. Mix them well with your hands after evenly distributing ¼ cup of brown sugar and ½ teaspoon of cinnamon over them.
To make the topping, mix the flour, oats, brown sugar, cinnamon, nutmeg, and salt in a separate basin. Toss in the melted butter and stir until the mixture becomes crumbly, using a fork or your fingertips.
Divide the crumbly topping evenly among the apples.
After 30–32 minutes in the oven, the apples should be tender and the topping should be brown.
Warm it up and top it with whipped cream or ice cream.
Extra Hint: If the butter is too hard to combine with the topping dry ingredients, heat the mixture in the microwave for ten to fifteen seconds to soften the butter.
Using oat flour in lieu of all-purpose flour will make it gluten-free
Enjoy!