1/2 lemon, juiced (recommend Meyer lemons if you have it)
1/4 – 1/2 shot simple syrup (depending on your sweetness preference)
1/4 – 1/2 shot limoncello (optional)
1 egg white
For a sugar rim, run a slice of lemon around the edge of the glass, then dip in sugar. Set glass aside. Or just garnish the glass with a lemon slice, whichever you prefer.
Combine vodka, triple sec, simple syrup, limoncello (if using), lemon juice and egg white in cocktail shaker without ice. Shake well. Then add ice and shake again to chill the cocktail. Strain into martini glass.
Shaking it without ice first seems to make it foamier and separate better (or maybe it’s just my imagination). If you don’t care then just shake it all together with ice the first time around.