In a mixing bowl, whisk the flour, baking powder, baking soda and salt together until well combined.
2¾ cup (330 g) all purpose flour, ½ teaspoon baking powder, ½ teaspoon baking soda, ½ teaspoon salt
Using a stand mixer fitted with paddle attachment or electric hand mixer with beaters, mix the granulated sugar, lavender buds and lemon zest together until they are the consistency of wet sand. Add tablespoon sliced of butter to the sugar. Cream the butter and lemon lavender sugar until well combined. This takes about 2 - 3 minutes on medium speed. 1½ cups (300 g) granulated sugar, 1 cup (226 g) unsalted butter, cubed, 2 teaspoons dried lavender buds, 1 tablespoon lemon zest
On low, mix in the egg, egg yolk, vanilla extract and lemon juice until smooth and well combined. Mix the dry ingredient into the wet ingredients until just combined. Cover the dough and chill in the fridge for at least 30 - 60 minutes. While the cookies chill, preheat the oven to 375 F (190 C).Line two large baking sheets with parchment paper. 1 large egg, room temperature, 1 large egg yolk, room temperature, 1 tablespoon (15 ml) lemon juice, 2 teaspoons (10 ml) vanilla extract
Scoop about 2 tablespoons (30 ml) of cookie dough onto the prepared baking sheet. Place the lemon and lavender cookie balls onto the lined baking sheet. Bake the lavender and lemon sugar cookies for 10 - 12 minutes. The bottom of the cookies will be very lightly golden brown. Remove the cookies from the oven onto a cooling rack. Within the first minute of removing the cookies from the oven, use a large biscuit cutter (wider than the cookies) to help shape any cookies back into a more round shape. Place the cutter over the cookies so the edges of the cookie are inside the cookie/ biscuit cutter. In a circular motion, gently nudge the edges back into a round shape. After 3 - 4 minutes, transfer the cookies off the hot baking sheet and onto the cooling rack to cool to room temperature.
Prepare the lemon lavender glaze by whisking the powdered sugar with lemon juice and lavender simple syrup. Top the lemon lavender cookies with the glaze and more lavender buds. Allow 30 - 45 minutes for the glaze to fully set and enjoy.
1½ cups (180 g) powdered sugar, 2 tablespoons (10 - 15 ml) lemon juice, 1 teaspoon lavender extract, optional