1. In a large bowl combine butter and sugar.
2. Beat in egg and vanilla and mix well.
3. Add flour, baking soda and cream of tartar to mixture and mix until smooth.
4. Divide dough into three equal pieces.
5. Work with one dough piece at a time, roll out on a lightly floured surface.
6. Using cookie cutters, cut out two equal sized heart shapes for each cookie.
7. Then using a smaller heart shaped cookie cutter cut out another heart in the center of one of the heart shaped cookies.
8. Spread the solid heart cookie with a little strawberry jam/jelly and place on cookie sheet, top with the second cookie (the one with the heart-shaped center cut out). The center of each cookie will reveal a red jelly heart.
9. Repeat process until all dough has been used.
10. Bake at 350 degrees for approximately 8 minutes or until golden.