In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.

In a large bowl, using an electric mixer, cream together the softened butter and 1.5 cups of granulated sugar on medium speed until light and fluffy, about 2-3 minutes. Beat in the egg and vanilla extract until well combined.

Gradually add the dry ingredient mixture to the wet ingredients, mixing on low speed until just combined. Be careful not to overmix the dough.

Cover the dough and refrigerate for at least 30 minutes. This helps the cookies hold their shape.

While the dough chills, preheat your oven to 375°F (190°C). Line two baking sheets with parchment paper. Place the remaining 0.25 cup granulated sugar for rolling in a small shallow bowl.

Scoop rounded tablespoons of dough and roll them into balls. Lightly press each ball to flatten it slightly, then create a small indent in the center with your thumb or the back of a measuring spoon. Fill each indent with about 1/4 teaspoon of raspberry jam. Roll the entire cookie ball in the granulated sugar, ensuring it's well coated.

Place the prepared cookies about 2 inches apart on the lined baking sheets. Bake for 8-10 minutes, or until the edges are lightly golden and the centers are just set. The cookies should still look soft.

Let the cookies cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely. Enjoy!