Prep - 15 minutes Cook - 15 minutes
Steam the green beans over 1 inch of boiling water, and cover.
Steam for a few minutes, or until tender, but still bright green.
While steaming, juice and zest the lemons.
Combine cooked beans, butter, lemon juice and lemon zest in a bowl and toss.
Season with salt and pepper.
Toss in the walnuts.