Preheat the oven to 350 degrees F.
Line baking sheet with parchment or silpat sheets
In a small bowl, combine the dry ingredients, whisk to blend.
Using a mixer, beat butter and sugar until light and creamy. Add egg yolks, lemon zest, lemon juice and vanilla and beat until well combined.
Add the flour mixture in 2 additions and beat just until moist clumps form.
Gather the dough together into a ball and wrap in plastic wrap.
Chill for 30 min-1 hour until dough firms up.
Pinch off the dough to form 1-inch balls. Place on the prepared baking sheets, spacing 1-inch apart. Use your floured index finger or 1/2 teaspoon measuring spoon press center of each ball making a depression. I use the end of a wooden spoon.
Fill each indentation with about 1/2 teaspoon of the jam mixture.
Bake until golden brown, about 20 minutes.
Transfer the cookies to wire racks to cool completely.