Preheat your oven to 350°F (175°C).
In a mixing bowl, combine the sliced apples, lemon juice, ground cinnamon, ground nutmeg, and granulated sugar. Toss to coat the apples evenly.
Transfer the apple mixture to a baking dish and spread it out evenly.
In another bowl, mix together the gluten-free rolled oats, almond flour, brown sugar, melted butter, and vanilla extract until well combined.
Sprinkle the oat mixture evenly over the apples in the baking dish.
Bake in the preheated oven for 45 minutes, or until the topping is golden brown and the apples are tender.
Let it cool slightly before serving. Enjoy!