Fill a saute pan or a frying pan with about 1/2 inch salted water; bring to a boil.
Add green beans, cover, and cook until green beans are tender to the bite, about 3 to 5 minutes, depending on how crisp you like your green beans.
In the meantime, melt butter in a nonstick frying pan over medium heat.
Add the zest and continue to cook for about 1 minute.
Drain the beans and wash under cold water until completely cooled.
Put the green beans back in the pan and pour the lemon butter over them; add lemon juice, salt and pepper, and toss to combine.
Transfer to a serving plate.
Garnish with parmesan cheese.
Serve.