With the rack in the middle position, preheat the oven to 350°F (180°C). Line two baking sheets with parchment paper or silicone mats.
In a bowl, combine the flour, baking powder and salt. Set aside.
In another bowl, cream the butter, sugar and vanilla with an electric mixer. Add the egg and beat until smooth. At low speed or with a wooden spoon, stir in the dry ingredients.
Shape the dough into balls using about 2 tbsp (30 ml) of dough for each cookie. Place 10 balls on each prepared baking sheet. With a fork, flatten the dough to create a criss-cross pattern. Sprinkle with coloured sugar crystals, if desired.
Bake one sheet at a time for 12 to 14 minutes or until the edges are lightly golden brown. Let cool completely.
The cookies will keep in an airtight container for 1 week at room temperature or 3 months in the freezer.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.