Preheat the oven to 350 degrees F.

Mix together the flour and salt.

Using a stand mixer, cream the butter and sugar together until the butter is soft and whipped. Add the eggs, and mix again until combined.

Add the vanilla, flour, and salt, and mix well.

Once the dough has chilled, shape the dough into 1" balls, then press down with your thumb in the center of the ball. Make a double thumbprint into each cookie to form a heart shape.

Fill the heart indents with jam, and bake for 12-14 minutes.

Form the dough into a disc, wrap in plastic wrap, and chill for 30 minutes.