Toss the blackberries with sugar, lemon zest, lemon juice, and cornstarch. Mix gently until evenly coated; set aside for about 30 minutes to allow the berries to macerate and release their juices while allowing the sugar to dissolve.

Preheat the oven to 350 degrees. Line a baking sheet with foil, for easier cleanup.

Coat 8 small ramekins or 4 large ramekins with coconut oil cooking spray and place them on the prepared baking sheet.

Combine the white sugar with the extracted vanilla bean seeds with your fingers until well combined.

Make the biscuit dough by combining the flour, vanilla sugar, baking powder, and salt; whisk until well combined.

Cut the butter into the flour mixture using your fingers until the mixture resembles coarse crumbs.

Make a well in the center of the dough then add the milk and beaten egg. Mix until just combined.

Stir the blackberries well then divide them evenly between the ramekins.

Drop spoonfuls of biscuit dough evenly on top of the berry-filled ramekins.