Prep the oven and pans: Preheat your oven to 350°F. Line two baking sheets with parchment paper. This prevents sticking and ensures even browning. Checkpoint: Your oven should reach temperature in 10–15 minutes and your pans are ready.

Combine dry ingredients: In a medium mixing bowl, whisk together 2 1/4 cups all-purpose flour, 1 teaspoon baking powder, and 1/2 teaspoon salt. Whisk for about 30 seconds until evenly distributed. Set aside. Checkpoint: You should not see any lumps of baking powder or salt.

Cream butter and sugars: In a large bowl, add 1 cup softened unsalted butter, 3/4 cup granulated sugar, and 1/4 cup light brown sugar. Using an electric mixer on medium speed, beat for 2–3 minutes until the mixture is pale, fluffy, and increased in volume. Stop and scrape down the bowl halfway through. Checkpoint: The mixture should look light and airy, not dense or grainy.

Add egg and flavorings: Add 1 large egg to the butter mixture and beat on medium speed for 1 minute until fully incorporated. Add 2 tablespoons fresh lemon juice, 2 tablespoons lemon zest, 1 1/2 teaspoons finely crushed dried culinary lavender, and 1/2 teaspoon vanilla extract. Beat for 1–2 minutes until everything is evenly combined and the mixture is light yellow. Checkpoint: The dough should smell strongly of lemon and lavender, with no visible streaks of unmixed ingredients.

Mix in dry ingredients: Reduce mixer speed to low. Add the dry ingredient mixture to the wet ingredients in two additions, mixing just until combined after each addition (about 30 seconds per addition). Do not overmix—stop as soon as you no longer see dry flour. Checkpoint: The dough should be soft, uniform in color, and hold together when gently squeezed, with no visible flour streaks.

Scoop dough: Using a rounded tablespoon or small cookie scoop, drop dough portions onto your prepared baking sheets, spacing them about 2 inches apart. You should have about 24 cookies. Gently flatten each mound slightly with the bottom of a glass or your fingertip. Checkpoint: All portions should be roughly the same size for even baking.

Bake cookies: Place baking sheets in your preheated 350°F oven on the middle rack. Bake for 11–13 minutes until the edges turn light golden brown but the very centers still look slightly underbaked and soft to the touch. Do not overbake. Checkpoint: The edges should be set and pale gold; the centers should jiggle slightly when you gently shake the pan.

Cool on pan: Remove baking sheets from the oven and let cookies rest on the hot pan for exactly 5 minutes. They will continue to cook gently from residual heat. After 5 minutes, use a spatula to transfer cookies to a wire cooling rack. Checkpoint: Cookies should be firm enough to move without breaking.

Cool completely: Leave cookies on the rack undisturbed for 15–20 minutes until completely cool to the touch. Checkpoint: Cookies should feel firm and crisp on the outside.

Prepare glaze: While cookies cool, in a small bowl whisk together 3/4 cup powdered sugar and 3 tablespoons fresh lemon juice until you have a smooth, pourable glaze (no lumps). Stir in 1/2 teaspoon finely crushed dried culinary lavender buds. Mix for 30 seconds until evenly distributed. The glaze should be the consistency of thin yogurt. Checkpoint: The glaze should drip slowly from a spoon and show tiny lavender specks throughout.

Glaze cookies: Using a small spoon or pastry brush, drizzle or brush glaze generously onto the top of each cooled cookie. Work in small batches so the glaze doesn't set too quickly. Checkpoint: Each cookie should have a light, even coating of glaze.

Set glaze: Place glazed cookies on a clean wire rack or parchment paper and let the glaze set undisturbed for 15–20 minutes at room temperature until it feels dry to the touch and no longer sticky. Checkpoint: The glaze should feel firm and no longer tacky when you gently touch it.