In a medium sized bowl, sift together flour and salt. Set aside.
In a large bowl, cream butter, sugar, and vanilla extract until light and fluffy. Beat in as much of the flour mixture as possible. Mix in the rest and gently knead till dough comes together. Wrap in plastic and chill for 30 minutes.
Roll out dough on lightly floured surface to ¼-inch thick. Cut into rounds with a 2-inch fluted cookie cutter. With half of the rounds cut a hole in the middle using small cookie cutters**. Place on ungreased baking sheet.
Pre-heat oven to 350°F (180°C). Bake cookies for about 20 minutes, until edges begin to brown. Allow cookies to cool to room temperature.
Spread jam or preserves on the flat side of each solid cookie. Dust cut-out cookie with powdered sugar and press the flat side onto solid cookie with jam or preserves in the middle and powdered sugar on the top.
**If you are using a linzer cookie mould, cut half of the rounds with small cookie cutter insert and the other half without the insert.