Bring a pot of water to boil. Fill a bowl halfway with ice water. Toss ramps into the boiling water and cook for 30 seconds to blanch. Using a slotted spoon, quickly remove ramps from boiling water and dunk into ice water to halt their cooking. Drain ramps and pat dry.

Pulse ramps, butter, lemon zest, and salt in food processor until well combined, about 30 seconds.

Divide butter mixture in half and wrap each half in a sheet of plastic wrap. Roll and shape each into a log. Twist ends of plastic to close.

Place logs in resealable plastic bags and freeze. Slice off rounds of butter as needed.