In a stand mixer fitted with the paddle attachment, cream together the softened butter, granulated sugar, and brown sugar on medium speed until light and fluffy, about 2 minutes. Add the egg and vanilla extract, and mix until combined.

In a separate bowl, whisk together the flour, baking soda, and salt. Gradually add the dry ingredients to the butter mixture, mixing on low speed until just incorporated. Avoid overmixing.

Wrap the dough tightly in plastic wrap and refrigerate for 30 to 45 minutes, until firm enough to handle.

While the dough chills, remove the strawberry jam from the fridge and let it come to room temperature. Stir it well to loosen its consistency.

Preheat your oven to 375°F (190°C). Line two baking sheets with parchment paper.

Scoop about 1.5 tablespoons of dough and roll it into a smooth ball. Place the balls on the prepared baking sheets, spacing them about 2 inches apart.

Using your thumb or the back of a round measuring spoon, gently press an indentation into the center of each dough ball. Be careful not to press all the way through to the bottom.

Spoon about 1/2 teaspoon of the jam into each indentation.

Bake the cookies for 9 to 11 minutes, until the edges are lightly golden and a toothpick inserted into the cookie (avoiding the jam) comes out clean.

Transfer the cookies to a wire rack and let them cool completely. Once cool, dust generously with powdered sugar.