Preheat your oven to 350 degrees F. In a medium bowl, gently toss the blueberries with the lemon juice, 2 tablespoons erythritol, and xanthan gum until the berries are evenly coated. Pour the mixture into an 8x8-inch baking dish and spread it out in an even layer.
In a separate bowl, combine the almond flour, 1/3 cup erythritol, and ground cinnamon. Add the cold butter pieces and use your fingertips to work the butter into the flour mixture until it resembles coarse, pea-sized crumbs.
Stir the chopped pecans into the crumble mixture. Scatter the topping evenly over the blueberries, making sure to cover the surface while leaving a few small gaps so steam can escape.
Bake for 30 to 35 minutes, until the topping is golden brown and the blueberry filling is bubbling around the edges.
Remove from the oven and let it rest for at least 10 minutes before scooping. The filling will thicken as it cools slightly.
Serve warm on its own or with a dollop of sugar-free whipped cream for the perfect finishing touch.
