Move the oven rack to the middle position and preheat oven to 350 degrees F. Line 2 baking sheets with parchment paper or Silpats. In a medium bowl whisk together the flour, baking powder, and salt. Set aside.
In a medium bowl beat together the butter and sugar on medium speed until creamy and the butter has lightened in color, about 2 minutes.
Add in the egg yolks, lemon zest, lemon juice, and vanilla and beat until just combined.
Add the flour mixture, and beat on low until the flour is absorbed.
Using a 1-tablespoon scoop, scoop the cookie dough onto the prepared baking sheets leaving 2 inches between cookie dough balls. Flour your thumb and make a shallow indentation in the center of each cookie dough ball. Bake the cookies for 10 minutes in the preheated oven.
While the cookies bake, add the jam to a small heat-proof bowl and microwave for 10-second intervals until the jam loosens and smooths out when stirred. After the cookies have baked for 10 minutes, remove them from the oven and reshape the center indentation using the back of a 1/2 teaspoon measuring spoon. Drop 1/2 teaspoon of raspberry jam into the center of each cookie. Pop the cookies back into the oven and bake for another 5-10 minutes, or until the cookies are light golden brown.
Let the cookies cool on the cookie sheet for 5 minutes before moving them to a wire rack to cool completely.