In a large mixing bowl, beat together the softened butter, granulated sugar, and brown sugar until the mixture is light and fluffy. This should take about 2-3 minutes using an electric mixer.
Next, add the egg and vanilla extract to the butter mixture. Beat until well combined. The egg helps bind the ingredients, and the vanilla enhances the flavor of the cookies.
In a separate bowl, whisk together the flour, matcha powder, baking powder, and salt. Make sure the matcha powder is evenly distributed throughout the dry ingredients to avoid clumps in the dough.
Use a cookie scoop or tablespoon to portion out the dough. Roll the dough into balls and place them on the prepared baking sheet, leaving about 2 inches of space between each cookie.
Bake the cookies in the preheated oven for 10-12 minutes or until the edges are golden brown. The centers will still be soft, but they will firm up as they cool.