Add the limoncello, vodka and bitters to a shaker with some ice.
2½ oz limoncello, 1½ oz vodka, 4 dashes lemon bitters
Rub a couple sprigs of thyme between your fingers and add it to the shaker.
4 sprigs fresh thyme
Shake to dilute, about 15-20 shakes.
Strain into two coupe glasses.
Top with seltzer.
6 oz seltzer
Garnish with more thyme and a lemon twist.
4 sprigs fresh thyme, lemon peel
Notes
The usual way to serve a spritzer is over ice. I just love the dressed-up feeling of these coupe glasses, but over ice in a tumbler is also great. If you want to change the glass, you may need to play around with the ratios depending on how big your glass is.