Add all ingredients into a shaker with ice and shake.
Strain into a coupe glass.
*Oleo saccharum sour mix: Using a vegetable peeler or similar tool, peel the entire surfaces of 1 grapefruit and 1 lemon into a bowl. Add 4 oz sugar and muddle, ensuring that the sugar is worked into the peels well. Let stand for 4 to 6 hours. Push the peels away to the sides of the bowl, allowing the oils to gather in the center. Remove the peels and transfer the oleo saccharum into a jar. Add 1/2 cup fresh lemon juice, seal and shake until fully combined. Chill before using.