Cream together softened butter and sugar in a large mixing bowl until the mixture is light and fluffy, with a pale color and a slightly grainy texture.
Add the egg to the creamed mixture and beat until well incorporated, resulting in a smooth, cohesive batter with a slight sheen.
Gradually sift and add the flour and baking powder to the wet ingredients, folding gently with a spatula until the dough just comes together and is soft but manageable.
Gather the dough into a ball, wrap it in plastic wrap, and chill in the refrigerator for about 30 minutes to make it easier to handle.
Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper for easy cleanup.
Remove the dough from the refrigerator and scoop small tablespoon-sized portions, rolling them into smooth balls between your palms to ensure uniform size.
Place the dough balls on the prepared baking sheet about 2 inches apart, pressing down gently with your thumb or the back of a spoon to create an indentation in the center of each.
Spoon or pipe a generous dollop of Nutella into the indentation of each cookie, filling it almost to the rim to achieve that glossy swirl.
Bake the cookies in the preheated oven for about 12 minutes until the edges are just golden brown and the Nutella filling is slightly bubbling and glossy.
Remove the cookies from the oven and allow them to cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely—they will be tender but set.
Enjoy these delicate, crumbly cookies with a rich Nutella center, perfect for sharing and indulging.
