Fresh Orange Tart with Hazelnut Crust

Whisk in both juices.

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.

Remove from heat.

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.

With blender running, add room-temperature butter 2 pieces at a time and process until blended.

Continue blending 3 minutes longer.

Transfer filling to bowl; mix in remaining 2 teaspoons orange peel.

Cover and chill overnight.

Butter 9-inch square tart pan with removable bottom.

Finely grind flour, sugar, nuts, and salt in processor.

Add butter and cut in using on/off turns until mixture resembles coarse meal.

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.

Preheat oven to 375°F.

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.).

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.

Garnish with candied blood orange slices.

Drizzle oranges with some of syrup.