Preheat oven to 375º F and grease a small rectangular baking dish (I used a 6-cup Pyrex dish, approximately 6"x8").
Combine apples, lemon, maple syrup, flour, flax, cinnamon, ginger, and salt in a large mixing bowl and then transfer to greased baking dish.
Using the same bowl for convenience, mix together oats, sugar, flour, walnuts, cinnamon, and cardamom. Stir in melted coconut oil and vanilla. Spoon crumble on top of apples in baking dish and place on center rack of oven. Bake until hot and top is golden brown, about 45-60 minutes.
Remove from oven and allow to cool slightly before serving. Serve with dairy-free yogurt or ice cream if desired.
This recipe originally appeared on GratefulGrazer.com.