Finely grate the lemon zest into a large bowl. Cut the lemon in half and squeeze in the juice from one half. Add 1 tablespoon of extra virgin olive oil and season with sea salt and freshly ground black pepper. Mix well. Put a pan of salted water on to boil. Meanwhile, trim the the beans. Once the water is boiling, steam or boil the beans until tender. Drain well, then tip the cooked beans into the bowl with your dressing and toss everything together, making sure all the beans get coated. Have a taste and squeeze over the remaining lemon juice if you think it needs it, then serve.