Preheat oven to 375 degrees. Line a baking sheet with parchment paper.
Thaw the puff pastry according to package instructions.
Gently toss together the raspberries, blackberries, sugar, flour, lemon zest, and salt until well combined.
Gently roll out the puff pastry using a rolling pin to be slightly larger then cut them into 8 squares.
Brush a thin layer of beaten egg on 2 joining sides of each square.
Divide the berry mixture between all squares then fold each square in half creating a triangle then gently seal the edges with your fingers or a fork. Transfer to the lined baking sheet.
Brush each turnover with the egg wash then sprinkle with some turbinado sugar. Cut a slit in the top of each turnover for ventilation.
Place into the oven and bake for 20-25 minutes, or until golden brown. Remove and allow to cool for a few minutes before serving. Enjoy!