I think Serban is right. Your specimen is a Coleoptera in the family Buprestidae. The species Julodis onopordi is a very polymorphic species, living around the Mediterranean sea. It has several subspecies. The subspecies found in Tunisia is Julodis onopordi ssp. koenigi (Mannerheim, 1837) but your specimen is lacking some white spots, looks like an old and worn out decolorated specimen or simply a variation. Check out this key.
The color of the body of Julodis fimbriata is usually green. The pronotum has a vertical white band on the dorsum not seen in the specimen from Tunisia.