Preheat your oven to 375°F (190°C). Prepare a baking sheet by lining it with parchment paper or lightly greasing it.
In a light-colored pan over medium heat, melt the butter until it turns golden in color. Be careful not to burn it. Once melted, transfer it to a mixing bowl.
To the melted butter, add brown sugar, vanilla extract, salt, and the egg. Beat the mixture until well combined and the sugar has dissolved.
Add the all-purpose flour, baking powder, and baking soda to the bowl. Combine the ingredients until you have a homogeneous cookie dough.
Wrap the dough in plastic wrap and place it in the freezer for 5 to 7 minutes to firm it up slightly.
In a small bowl, mix the remaining brown sugar and granulated sugar.
Remove the chilled dough from the freezer. Take portions of the dough and roll them into balls. Roll each ball in the sugar mixture until coated.
Place the coated dough balls onto the prepared baking sheet, leaving space between them. Bake in the preheated oven for about 10 minutes or until the edges are golden brown.
Remove the cookies from the oven and allow them to cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.