In a small bowl (or your mixing bowl) rub together the lemon zest, lavender flowers, and granulated sugar until a sand-like mixture forms. This releases the oil in the zest to infuse the lemon flavor throughout.

In the bowl of a stand mixer, add the lemon zest and sugar mixture, powdered sugar, and room temperature butter. Cream together butter and sugars until pale in color and fully combined (like a paste). Add oil, eggs, vanilla extract, and lemon juice, mixing until combined.

In a separate bowl, sift together flour, cream of tartar, baking soda, and salt. Mix the combined dry ingredients into wet ingredients until just combined.

Chill the dough for at least 30 minutes. This helps the flavor and texture develop - I highly recommend this!

20 minutes before baking, preheat the oven to 350°F and line a sheet pan with parchment paper. If making the lavender sugar, combine granulated sugar and lavender into a small bowl for later.

Dollop a scoop (#40 scoop) or about 1 ½ tablespoons of batter about 2 inches apart on the prepared baking sheet. Dampen a flat-bottomed glass with water, then dip in a small bowl of granulated sugar. Gently press each cookie dough ball with the bottom of the glass approximately halfway down, about ½ inch thick. Dip the glass back in the sugar between each cookie to recoat. I also like to add a sprinkle of the sugar mixture on top for good measure.

Bake for 8-10 minutes, or until cookies are just beginning to barely turn golden brown around the edges. See notes below about baking sheet type.

Let the cookies cool for a few minutes on the baking sheet until set up enough to transfer to a cooling rack. Store cooled cookies in an airtight container at room temperature for up to 4 days.