In a medium bowl, sift together flour, powdered sugar, and baking powder.

Cut in butter with a pastry blender or fork until mixture resembles corn meal.

Mix in egg and yolk, working until it forms a rough dough.

Add almond flour and knead until it forms a smooth dough.

On a piece of parchment paper, roll dough out to 1/4" thickness.

Place in a 9-inch tart pan, fitting dough evenly down into pan.

Press bottom and sides lightly to ensure dough is filling whole pan.

Prick dough all over the bottom with a fork.

Cover with plastic wrap and refrigerate for at least 30 minutes.

While dough is chilling, preheat oven to 350 degrees.

Remove dough from refrigerator and bake for 12 minutes, just until it's starting to brown on the edges.

Remove from oven and allow to cool.

Combine egg yolks, 2 Tablespoons sugar, and cornstarch in a small bowl.

Stir gently to mix, being careful not to incorporate any air. Set aside.

In a heavy sauce pan, bring milk, cream, remaining sugar, and vanilla bean to a boil.

Pour one third of milk mixture into egg mixture, stirring constantly.

Return to sauce pan over medium low heat.

Add zests.

Stir continuously.

When mixture starts to thicken, switch to a whisk and continue to cook for another 1-2 minutes or until thickened.

Turn off heat and whisk in butter.

Remove vanilla bean.

Pour into a flat pan and cover immediately with plastic wrap, making sure the plastic wrap touches the top of the pastry cream.

Refrigerate at least 30 minutes, or until cool.

Remove tart shell from pan.

Pipe pastry cream into shell.

Top as desired.