18 lemons (Meyer or Eureka; see Notes), washed and dried
One 4-in. rosemary sprig, washed and dried
2 bottles (750 ml. each) 100-proof vodka, such as Stolichnaya or Smirnoff
4 1/2 cups sugar
1. Peel lemons with a sharp vegetable peeler, taking only the zest (top layer) and avoiding any white pith. Put rosemary in a 1-gal. glass or ceramic container with a tight seal. Add zest to jar.
2. Pour 750 ml. vodka over rosemary and zest; seal container. Let sit undisturbed in a cool, dark place for 40 days.
3. In a saucepan, bring 5 cups water to a boil and add sugar. Cook, stirring, until sugar has dissolved. Let sugar syrup cool to room temperature, about 1 hour.
4. Pour syrup and remaining 750 ml. vodka over lemon-vodka mixture, stir, and seal container. Let sit in a cool, dark place for another 40 days.
5. Pour limoncello through cheesecloth into a large spouted pitcher and divide among gift bottles.