Preheat Oven: Set oven to 350°F (175°C) and line baking sheets with parchment paper.
Mix Dry Ingredients: In a medium bowl, whisk together flour, baking soda, baking powder, and salt.
Cream Butter & Sugar: In a large bowl, beat butter and sugar with an electric mixer until light and fluffy (2–3 minutes).
Add Egg & Vanilla: Mix in egg and vanilla extract until smooth.
Combine Wet & Dry: Gradually add dry ingredients to wet ingredients, mixing until just combined.
Shape Cookies: Scoop dough into 1-inch balls and roll in granulated sugar. Place on baking sheets about 2 inches apart.
Bake: Bake for 8–10 minutes until edges are set but centers look soft.
Cool: Let cookies rest on the sheet for 5 minutes, then transfer to a wire rack to cool completely.