Whisk together cornstarch, flour, salt, baking powder, cinnamon, and red pepper in a bowl.

Combine butter and sugar in a stand mixer; beat until light and fluffy.

Reduce speed to medium and add egg yolks, one at a time, beating well after each addition.

Mix in orange juice and vanilla extract.

Add flour mixture and beat until combined.

Turn dough out onto a lightly floured surface and press into a rectangle.

Wrap dough tightly with plastic wrap and chill for 1 hour.

Preheat oven to 350°F (175°C).

Line baking sheets with parchment paper.

Divide dough in half.

Roll half of the dough to 1/4-inch thickness on a well-floured surface.

Cut into 40 cookies with a 2-inch round cookie cutter, rerolling scraps as needed.

Arrange cookies 1/2 inch apart on prepared baking sheets.

Bake for 10 minutes, or until cookies are set.

Let cool completely on wire racks.

Repeat with remaining dough.

Flip 20 cookies over.

Top each with 1 1/2 teaspoons of dulce de leche.

Top with remaining cookies.

Sift powdered sugar evenly over the sandwiched cookies.