Finely chop the white part of the onion and sauté over low heat in a pan in olive oil and a little salt until they are transparent.
Add the celery and let it cook on a low heat 10-15 minutes at all times. The celery should be al dente.
At the last add the shelled shrimp and let them cook a few minutes. They should not be overcooked!
Serve immediately or at room temperature with lemon zest, a little fleur de sel and ground pepper.