Preheat your oven to 375°F (190°C) and line a baking sheet with parchment paper.

Soften the butter in a microwave-safe bowl for about 20 seconds.

In a mixing bowl, cream together the softened butter, granulated sugar, and brown sugar until smooth.

Beat in the egg and vanilla extract until well combined.

Gradually stir in the flour and salt, mixing until just incorporated.

Using a 1 tablespoon cookie scoop, create small balls of cookie dough and roll them in the optional sugar.

Place the cookies on the prepared baking sheet and make a small indentation in the center of each cookie.

Fill each indentation with about 1 teaspoon of raspberry jam.

Bake in the preheated oven for 8 minutes, removing them before they brown too much.

Allow cookies to cool on the baking sheet for about 5 minutes before transferring them to a cooling rack.