Preheat the oven to 350°F(177C°). Line baking sheet with parchment paper or silicone baking mat. Set aside.
Combine flour, salt and sugar in a medium bowl and set aside.
Place the butter in a large bowl and beat on medium speed for 1 to 2 minutes until it is soft with a hand-held mixer or with paddle attachment if using a stand-mixer. Add the egg and mix well. Stop the machine and scrape down the sides of the bowl with rubber spatula to be sure they are all mixed.
Add in the flour mixture and mix well until the dough comes together.
Take 25 gram pieces ( a little bit more than 1 tablespoon can take) of the dough and roll them into balls. Alternatively, you can divide the dough equally into 20 pieces and roll each into a ball as this recipe makes 20 cookies. Press the balls preferably with a flat-bottomed glass or a measuring cup to flatten them evenly or with the palm of your hand.
Glaze the cookies with milk or egg wash them by mixing 1 egg yolk with 1 teaspoon of water. Sprinkle the sunflower seeds on top of them.
Bake for 15 minutes until the edges change color. Remove the cookies from the oven and let them cool for 15 minutes on the baking sheet before transferring them to a wire rack to completely cool.