Line two baking sheets with parchment paper, or use a silicone baking mat.
In a stand mixer, beat the butter and sugar together until light and creamy—about 2 minutes.
Add in the vanilla extract.
While mixing, slowly add in the flour until just incorporated.
Use a cookie scoop (or your hands!) to portion out the dough on the prepared cookie sheets, about 1" apart. You should be able to make 35–40 cookies from the dough.
Use an inverted tablespoon to press down on the top of the cookies, flattening them and making a small dip in the center of each cookie.
Bake the thumbprint cookies for 12-15 minutes, until lightly golden brown.
Immediately after baking, press the tablespoon back into each indent, as they likely will rise back up a bit during baking and won't be quite deep enough.
Cool the cookies on the cookie sheet for about 15 minutes.
Fill each cookie thumbprint with approximately 1 to 1 ½ tsp of jam.
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