Preheat the oven to 350F and line an 8x8 baking pan with parchment paper. Set aside.
In a bowl, mix together the butter and sugar until combined.
Add egg and vanilla until fully mixed.
Add flour and salt to the bowl. Fold into the mixture until combined.
Evenly spread the batter into the baking pan.
In a bowl, stir together sugar and cinnamon for topping. Sprinkle on top of the cookie batter and bake for 25-30 minutes or until the cookie is lightly browned but not hard and over-baked.
Remove from the oven and allow to cool in the pan for 10-15 minutes before removing and cut into 12 bars.