Preheat oven to 400. Cover a baking sheet with foil and set aside.
Pulse almonds in food processor with 2 tablespoons of sugar until finely ground. Add flour and salt and pulse just until combined. Set aside.
Beat butter 6 tablespoons of sugar in mixer at high speed until light and fluffy. Add vanilla, then eggs, beating well after each. Reduce speed and add almond / flour mixture and beat just until combined.
Divide batter among gratin dishes. Place blackberries on top and press lightly into batter, then sprinkle tops lightly with sugar. Place on baking sheet and bake until firm and golden brown with slightly darker edges, approximately 20 minutes. Allow to cook on rack for about 10 minutes. Serve warm.