Combine flour, 1 cup sugar, orange sugar, baking powder, pinch of salt, egg and cubes of the very cold butter in large bowl.
Using pastry cutter or fingers/fork, combine roughly until butter is incorporated slightly. The final texture should be like pebbles.
Split mixture in half into separate bowls. Add brows sugar to one bowl and toss to mix. Set this bowl aside.
Press the mixture (without brown sugar) into the pan and press down to form bottom crust.
In a new bowl, combine berries with sugar, cornstarch, zest and juice of citrus fruit and toss well. Let sit for a few minutes to incorporate the starches well.
Add berries into pan on top of bottom crust.
Roughly cover berries with the brown sugar flour mix.