Preheat oven to 350 degrees F (175 degrees C). Grease cookie sheets.
In a large bowl, cream together butter and sugar until smooth. Beat in egg and vanilla. Gradually blend in the flour and salt. Roll dough into 1 inch balls and place onto the prepared cookie sheets.
Make a thumbprint in the center of each cookie and fill with about 1/4 teaspoon of jam.
Bake for 12 to 15 minutes in the preheated oven, or until cookies are golden brown.
Allow cookies to cool on baking sheet for 5 minutes before transferring to a wire rack to cool completely.
Interesting Facts
Thumbprint cookies originated in Germany in the 18th century.
The name “thumbprint” comes from the indentation made in the center of the cookie when made.
Thumbprint cookies are popular during holidays, such as Christmas and Easter.