Preheat oven to 350 degrees.
Mix dry ingredients in a medium-sized bowl: flour, salt, baking powder, baking soda. Set aside.
Using an electric mixer, mix wet ingredients: butter, sugar, vanilla, egg, orange zest, and orange juice.
Slowly add dry ingredients to the wet ingredients.
grease or line an 8x8 baking dish with parchment paper.
Pour cookie batter in baking dish and spread out evenly.
Bake for 25-30 minutes.
Remove from oven. Let cookies cool. Sift powdered sugar on top of the bars and serve.