Preheat oven to 375 degrees Fahrenheit. Grease a deep dish pie plate with butter or coconut oil and set aside.

In a large mixing bowl, toss the apple slices and cranberries with the 1/2 cup demerara sugar. Spread into the prepared dish.

In another large mixing bowl, stir the flour, oats, remaining sugar, cinnamon, and sea salt. Cut the butter up into chunks and cut it into the dry ingredients with a pastry blender or two knives, working the butter in until you have small chunks of it throughout.

Sprinkle the topping over the fruit and bake, uncovered, for 45-50 minutes, or until fruit is tender and the topping is crisp and lightly browned.

Cool for at least 10 minutes before serving.