Sift flour, baking soda, and salt in small bowl and set aside.
Cream butter and sugar till light and fluffy. Beat in egg and vanilla. Stir in flour mixture, half at a time. Blend well to make soft dough. Chill.
Roll dough into in tablespoon-sized balls. Roll each ball in sesame seeds*, then place on greased cookie sheet 3” apart. Bake 350° for 10 minutes, until barely golden. Cool slightly, then transfer to wire rack to cool completely.
*I like to roll just half of each ball in seeds. Bake plain-side down. For me, this hits the sweet spot of buttery cookie and bitter seeds.
