Preheat the oven to 325°F.
In a mixing bowl, whisk together the flour, baking powder and salt. Set aside.
In a stand mixer, fitted with the paddle attachment, cream the butter and sugar until light and fluffy, about 2 minutes.
Add the eggs and vanilla and stir until completely combined.
Add the flour mixture and mix just until combined.
Line 2 baking sheets with parchment paper or a Silpat.
Using your hands, roll the dough into balls, about the size of a golf ball and place them, an inch apart, onto the prepared baking sheets.
Dip your thumb (or index finger if easier) into flour and then press into the cookies to create a heart design.
Fill each of these with a small amount of jam and then transfer the baking sheets to the refrigerator to chill for 30 minutes.
Bake the cookies until they are very lightly browned on the edges, about 16 minutes.
Allow the cookies to cool on the pans for 10 minutes and then transfer to a wire cooling rack to cool completely.
