Preheat oven to 350 degrees F.

In a bowl, combine filling ingredients. Xanthan gum should be lightly sprinkled while mixing so that it's evenly spread and doesn't clump. Set bowl aside.

In another bowl, combine walnuts, coconut flour, flaxseed meal, 1/4 cup sweetener, sea salt and toss together so it mixes evenly.

Add butter and combine until the whole mix is crumbly.

Set 1/2 cup of the crumble aside and the final another 1 tsp sweetener to it.

Grease a 9-inch glass pie dish with butter, then press down the bowl of crumble. Use your hands to press it flat into the bottom.

Pour the fruit mixture over the crust and spread evenly.

Finally, sprinkle the remaining 1/2 cup of crumble over the pie.

Bake for about 20 minutes covered with tinfoil, then a final 10-20 minutes until crumble is browned.

Once finished, let cool completely in the refrigerator (at least a few hours to set so it can be sliced and held like a pie), then serve.