Don't do it. Contrary to popular Day-Crawler belief, you should never use a romantic gesture to apologize after an argument or a fight. This will only taint your future romantic gestures for some time to come. Instead, simply give a sincere apology and put any and all romance on hold until the both of you have cooled down a bit or maybe after a week. Then pick up where you left off. Giving a peace offering of flowers or a gift to win back sympathy is a cop-out and if you think about it...rather insulting to insist that one's affections can be won by gifts.