Likely targeted, check under Rewards > My cashback to see if applicable to your account.
T&Cs:
Spend $1,500 or more in a single transaction on your Citi Mastercard Credit Card by 1 Dec 2024. Offer eligible for online payments only. Payments must be made within Australia in AUD. Offer cannot be used in conjunction with any other offer. Excludes voucher codes, gift cards, cash back and coupon deals. Offer is valid when shopping online directly via Cathay Pacific website.
https://files.ozbargain.com.au/upload/100415/116179/screensh…
It does have those lists of exclusions including cash backs, but I'm not sure they would be relevant as citi wouldn't necessarily know about them (Think this is a boilerplate copied T&Cs). You would still need to so on Cathay Australian website and in AUD i'd say.