Preheat the oven to 350°F. Line baking sheets with parchment paper.
Whisk together the flour and salt, set aside.
Using a stand mixer or a handheld mixer (if using a handheld mixer make sure to use a large mixing bowl) Cream the butter and sugar at medium speed until light and fluffy, about 2 minutes. Scrape down the sides of the bowl with a rubber spatula.
Reduce the mixer speed and add the egg, almond, and vanilla extract. Mix until well combined, about 1 minute. Scrape down the bowl again.
Lower the speed, add the flour mixture in 4 separate batches, mixing after each and ensuring to scrape down the sides and bottom of the bowl. Mix until a dough forms. Knead by hand if necessary.
Roll out the dough to ¼ inch thickness. Use a 2.5 inch round cookie cutter to cut out circles. Use a smaller cutter to create windows on half of the circles. Place on the parchment lined cookie sheet.
Position it on the center rack of the oven to ensure even baking, avoiding placement too close to the top or bottom. Bake for 10-11 minutes until just set. If you push on the top of the cookie it should feel a bit firm- not doughy. Cool on the baking sheets.
Place a heaping teaspoon of strawberry jam on top of the solid circle, top with the cut out cookie. Sprinkle with powdered sugar if desired.
See Storage instructions below and in post