In a blender, combine 1/2 cup simple syrup (made with 1 1/2 parts sugar to 1 part water) with the rind of 1 preserved lemon, pith removed; 2 large sprigs thyme; and 2 crushed juniper berries. Blend until very smooth, about 2 minutes. Strain through a fine sieve into a small bowl; discard solids.
In a cocktail shaker, combine 2 ounces London dry gin, 3/4 ounce fresh lemon juice, 1/4 ounce Luxardo Maraschino liqueur, 1/2 ounce freshly pressed beet juice, and 1/2 ounce preserved lemon syrup. Fill with ice and shake vigorously until cold. Fill a rocks glass with ice and strain cocktail into glass. Garnish with beet greens and a beet slice.
If you want to go fancy, try Zerrip's garnish: gelatin foam made from beet juice, Luxardo Maraschino liqueur, and a gelatin sheet.
Recipe by Andrew Zerrip, head bartender at Olmsted in Brooklyn, New York.