Whisk together almond flour and sugar in a large bowl. Cut in butter with a pastry cutter or two knives until well mixed. Stir in heavy cream, egg and almond extract until soft wet dough forms. Set aside.
Stir together blackberries, sugar, cornstarch, lemon zest and juice, nutmeg and salt until evenly blended. Pour into a 9 1/2-inch pie dish.
Spoon dough mixture over blackberries in pie dish until blackberries are covered, leaving a 1-inch border around edge of pie dish. Bake until berries are bubbling and cobbler topping is golden brown, 40 to 45 minutes. Transfer pie dish to a wire rack and let cool slightly.