While the tart shell is baking, make the panna cotta. Once the panna cotta has reached room temp, pour it into the cooled tart shell and transfer the tart to the fridge. Chill for 3 hours or overnight.
Arrange the blood orange segments in a star-formation in the center of the set panna cotta tart. Pour the room temperature gelée in the center of the star-formation until it covers the surface of the tart.
Place the gelatine leaf in a bowl of water and set aside to gel. Pour the blood orange juice and sugar into a saucepan and bring to a simmer. Take the juice off of the heat.
Squeeze the gelatine to remove any excess water. Place the gelatine leaf in the juice mixture and stir until dissolved. Pour the gelée in the center of the star-formation until it covers the surface of the tart.