Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

In a large mixing bowl, cream together the softened butter and powdered sugar until light and fluffy, about 3-4 minutes.

Mix in the vanilla extract until well combined.

Gradually add the flour and salt, mixing until the dough comes together. It should be soft but not sticky.

Scoop out about 1 tablespoon of dough and roll it into a ball. Place it on the prepared baking sheet. Repeat with the remaining dough, spacing the cookies about 2 inches apart.

Using your thumb or the back of a teaspoon, make an indentation in the center of each cookie.

Fill each indentation with about 1/2 teaspoon of fruit jam. If desired, sprinkle chopped nuts around the edges of the jam.

Bake in the preheated oven for 12-15 minutes, or until the edges are lightly golden.

Remove from the oven and let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.