Preheat oven to 350°. Grease a 9″x 13″ baking pan.
Using an electric mixer, beat butter, brown sugar, and sugar until fluffy. Add baking soda, cinnamon, and salt, and mix until combined. Add eggs and vanilla, and mix just until combined. Add flour, mixing on low speed until combined.
Transfer dough to prepared pan, spreading evenly. Bake 30 minutes, or until set and lightly golden.
Sprinkle warm bars with cinnamon-sugar. Cool completely before cutting into bars.
*To make your own cinnamon-sugar, combine 1/2 cup sugar and 1-2 tablespoons cinnamon. Store in airtight container.