Preheat the oven to 350 F, and line a baking sheet with a silicone non-stick mat.
In a medium bowl, beat the butter and brown sugar together until light and fluffy, about 1 minute.
Add the egg and beat until combined.
In a separate bowl, whisk together the flour, baking powder and salt.
Slowly add the flour mixture to the butter mixture while beating continuously. Do not over mix, but make sure there are no streaks of flour remaining.
Stir in any additional things you may like: orange zest, chocolate, etc.
Scoop teaspoon-sized dough balls onto the baking sheet.
Pour the coarse sugar into a small dish, and roll each cookie dough ball in it. Place the dough balls back on the baking sheet, evenly spaced.
Bake the cookies for 10 minutes.
Let the cookies cool for 5 minutes on the baking sheet, and then move to wire rack to cool completely.