Preheat oven to 350F. Line a 9-inch square baking pan with aluminum foil.
In a large bowl, cream together butter and sugar until light. Beat in salt, egg and vanilla extract until well combined. Add in flour and stir until combined.
Press dough into prepared baking dish and smooth it into an even layer.
Stir together sugar and cinnamon for topping. Sprinkle over dough evenly.
Bake for about 40 minutes or until bars are set and the edges are just very lightly browned. Cool in the pan before slicing.