Combine first 3 ingredients; set aside.
Beat sugar and butter at medium speed with an electric mixer until light and fluffy. Add egg, and mix until well blended. Add flour mixture, and mix until well blended. Stir in lemon juice, vanilla, and sesame seeds. Drop by tablespoonfuls onto baking sheets lined with parchment paper.
Bake at 350° for 8 minutes or until lightly golden. Cool slightly on baking sheets; remove to wire racks to cool completely. Store in an airtight container until ready to serve.