Preheat oven to 350 degrees. Butter an 8x8 baking dish.
Toss nectarines, blueberries, lemon juice, sugar and tapioca starch in baking dish until evenly coated.
In a medium bowl, combine oats, almond flour, pecans, brown sugar, cinnamon and salt. Cut in butter with a pastry cutter until mixture resembles coarse crumbs. Sprinkle the mixture evenly on top of fruit.
Bake for 40-45 minutes until fruit is bubbling and top is lightly golden brown.
Transfer to a wire rack to cool for 10-15 minutes. Serve with vanilla ice cream or fresh whipped cream if desired.