Whisk the flour, baking powder, confectioners' sugar, cinnamon, and salt in a medium bowl and set aside.

In a stand mixer fitted with the paddle attachment, combine the softened butter and granulated sugar. Beat on medium speed until fluffy, then add the vanilla extract and egg.

Reduce the mixer speed to low and slowly incorporate the flour mixture until just combined.

Divide the dough into two portions, shaping each into a disk. Wrap in plastic wrap and refrigerate for at least 2 hours.

Preheat your oven to 375°F (190°C) and line two baking sheets with parchment paper.

Roll out one disk of dough on a lightly floured surface to about 1/8-inch thickness.

Cut out 2-inch fluted cookie shapes, and for half, cut out hearts in the center using a smaller ½-inch cutter.

Place the cookies 2 inches apart on the prepared baking sheets and chill for 5 minutes.

Bake the cookies for 8 to 10 minutes or until pale golden, rotating the pans halfway through the baking time.

Remove from the oven and let cool completely on wire racks.

While the cookies are cooling, heat the strawberry jam in a small saucepan over medium heat until it reduces to a thick consistency, about 7 minutes. Let it cool.

Dust the cookies with cut-out centers with confectioners' sugar and spread jam on the uncut cookies. Top with the sugared cookies to form sandwiches.