Cream the butter and powdered sugar. Add hazelnut powder and mix.
Add egg yolks, then mix in flour, baking powder, and salt.
Do not overmix. Form a dough, wrap in plastic, and chill overnight.
Next day, roll out the dough and line 6 tart rings (8 cm x 2 cm).
Chill for 6 hours or freeze before baking.
Lemon-Yuzu Cream Domes
Hydrate gelatin in water.
Heat citrus juices and water.
Whisk eggs, sugar, and cornstarch in a bowl.
Gradually pour hot liquid into the egg mix while whisking.
Return to heat and cook until boiling; continue for 1 more minute.
Add gelatin. Cool to 50°C, then add butter and emulsify with a stick blender.
Pour into 6 cm hemisphere molds and freeze for at least 6 hours.