Preheat oven to 400 degrees.
In a medium bowl whisk together the flour, sugar, baking powder and salt. Add in cubed butter and with a pastry blender combine until mixture is coarse and crumbly. Gently fold in the blackberries, lemon zest, and lemony thyme. Make a well in the center and reserve.
In a small bowl whisk together cream and eggs. Pour into the flour mixture and stir until moistened.
Pour out onto a well floured surface and gently knead just until mixture comes together, about 7-8 times. It will still be crumbly around the edges.
Transfer to a parchment lined baking sheet and form into a circle about 3/4-inch thick. Cut into 8 wedges and separate them slightly. Brush with cream and sprinkle with sugar. Bake for 15 - 18 minutes or until golden brown. Transfer to a rack to cool.