In a medium-sized bowl, whisk together the flour, baking powder, and salt, then set aside.

In the bowl of an electric stand mixer or using a handheld mixer, beat the dairy-free butter and sugar until creamy. Add in the egg and lemon zest and continue beating until well combined.

Add the dry ingredients to the bowl and beat on low until the dough starts to come together, scraping down the sides of the bowl with a spatula as necessary. The dough will be quite soft. Chill the dough for 30 minutes before baking to prevent the cookies from overspreading in the oven and to make them easier to roll.

Preheat the oven to 180°C (350°F) and line 2 trays with baking paper. Using lightly floured hands, roll tablespoons of dough into balls and place them evenly on the trays, allowing enough room between them to spread.

Using your thumb or a ½ teaspoon round measuring spoon, press an indent into the top of each cookie ball, pushing the edges out slightly. Fill the indent with ¼ - ½ teaspoon of the lemon butter. Repeat with all cookies.

Bake for 10-12 minutes or until the edges just start to get a bit of color. Let cool on the tray for 10 minutes to firm up before transferring to a wire rack to cool completely.

Make the glaze by mixing the icing sugar with a little lemon juice until the icing is just thin enough to drizzle over the cookies. Either drizzle over cooled cookies with a spoon or add to a piping bag with a small round piping tip attached. Let the glaze set and harden before storing cookies in an airtight container for up to 4-5 days.