1. Preheat the oven to 375°F (190°C).
2. Grease a tart pan with butter or coconut oil.
3. In a bowl, mix almond flour, oat flour, melted butter or coconut oil, maple syrup, and vanilla extract until a dough forms.
4. Press the dough evenly into the tart pan to form the crust.
5. Bake the crust for 10-12 minutes until slightly golden, then let it cool.
6. Peel, core, and thinly slice the apples.
7. In a bowl, toss the apples with cinnamon, sugar, and lemon juice.
8. Optionally, pre-cook the apple mixture in a pan over medium heat for 5-7 minutes until slightly tender.
9. Arrange the apple slices in an overlapping pattern over the cooled crust.
10. Bake for 35-45 minutes until the apples are soft and the edges are golden brown.
11. Optionally, drizzle caramel sauce or glaze over the baked tart for extra sweetness.
12. Allow the tart to cool slightly before serving.
13. Serve warm or at room temperature with whipped cream, ice cream, or powdered sugar.
14. Store leftovers in the refrigerator for up to a few days.
15. Enjoy your homemade gluten-free apple tart!