Fresh Orange Tart with Hazelnut Crust

Ingredients

• 1.3 cups flour 
• 1 slices blood oranges 
• 1 large egg yolk 
• 4 large eggs 
• 1.3 teaspoons gelatin powder unflavored
• 0.3 cup hazelnuts 
• 3 tablespoons juice of lemon fresh
• 2 teaspoons lemon zest finely grated
• 0.8 cup orange juice fresh
• 2 tablespoons orange zest finely grated
• 0.5 cup powdered sugar 
• 0.3 teaspoon salt 
• 1 cup sugar 
• 9 tablespoons butter unsalted chilled cut into 1/2-inch cubes
• 1 tablespoon water 

Equipment

• bowl
• frying pan
• sauce pan
• oven
• whisk
• blender
• kitchen thermometer
• tart form

Directions

1. Sprinkle gelatin over 1 tablespoon water in small bowl.
2. Let stand 10 minutes to soften.
3. Combine sugar, 2 tablespoons orange peel, and lemon peel in medium metal bowl. Using fingertips, rub ingredients together until sugar is moistened.
4. Add eggs; whisk until smooth.
5. Whisk in both juices.
6. Place bowl over saucepan of simmering water (do not allow bottom of bowl to touch water); whisk constantly until mixture thickens and thermometer inserted into mixture registers 180°F, about 5 minutes.
7. Remove from heat.
8. Add gelatin mixture and stir until dissolved. Strain orange mixture into blender; let cool until thermometer inserted into mixture registers 140°F, about 10 minutes.
9. With blender running, add room-temperature butter 2 pieces at a time and process until blended. Continue blending 3 minutes longer.
10. Transfer filling to bowl; mix in remaining 2 teaspoons orange peel. Cover and chill overnight.
11. Butter 9-inch square tart pan with removable bottom. Finely grind flour, sugar, nuts, and salt in processor.
12. Add butter and cut in using on/off turns until mixture resembles coarse meal.
13. Add egg yolk and blend in using on/off turns just until moist clumps form (do not allow dough to form ball). Press dough onto bottom and up sides of prepared pan (crust will be about 1/4 inch thick). Using thumb, press around sides to extend crust 1/4 inch above edge of pan. Chill 1 hour.
14. Preheat oven to 375°F.
15. Bake crust until golden brown, about 20 minutes. Cool crust completely on rack. (Crust can be made 1 day ahead. Store airtight at room temperature.)
16. Stir orange filling to loosen. Spoon enough chilled orange filling into crust to fill completely. Chill tart at least 1 hour and up to 4 hours.
17. Garnish with candied blood orange slices.
18. Drizzle oranges with some of syrup.
19. Serve cold.