すみません、パクチーを抜いていただけますか？ — Excuse me, could you please remove the cilantro? (Restaurant, Formal — to staff, JLPT N3)

Gesture & etiquette

Look at the menu, then make eye contact with the staff.

Be polite. If you have severe allergies, it's better to carry an allergy card in Japanese or use a translation app to explain fully. Just saying 'nuki' (omit) is for dislike or mild intolerance.