Combine blackberries, 1 tbsp. granulated 1:1 sweetener, ¼ tsp. stevia, lemon juice and xanthan gum in bowl and mix well with a fork, lightly smashing some of the blackberries until they become jammy. Divide the blackberry mixture between ramekins or transfer to an oven safe skillet (8-inch or smaller) or small baking dish (around 16-oz. volume would work best).
In a separate bowl, mix the ingredients for the crumble together. Start by melting the butter. Mix ingredients together until a crumbly dough dough starts to form.
Using a spatula or spoon break up the dough and top the blackberry filling with the crumble.
Bake for 15-20 minutes or until the berries begin to bubble and the top is golden brown.
Allow to set for 5-20 minutes before serving.
Store in an airtight container in the fridge for up to 5 days.