Preheat your oven to 350°F (175°C).
In a large bowl, combine the sliced apples with lemon juice, cinnamon, and nutmeg. Toss to coat evenly.
Transfer the apple mixture to a greased 9x13-inch baking dish, spreading it out evenly.
In another bowl, mix together the almond flour, oats, chopped nuts, melted coconut oil, vanilla extract, and erythritol until well combined.
Sprinkle the oat mixture over the apples, ensuring an even layer covers them.
Bake in the preheated oven for 30-35 minutes, or until the apples are tender and the topping is golden brown.
Remove from the oven and let it cool for a few minutes before serving warm or at room temperature.