The Welsh midfielder opened the scoring in the first half by heading home an inviting cross from Mesut Ozil.
Arsenal were put under pressure by the hosts in the second half but late goals from Mathieu Flamini and Ramsey earned the Gunners the three points.
Below, Sports Mole takes a look at the key talking points from the match.
On target 4
On target 6
Was the result fair?
Yes, but 3-0 might be considered quite flattering on Arsenal. The visitors dominated possession for long periods, as they often do, but they were not at their best today. On a different day it could have been more difficult but Arsenal battled well for the victory.
Manager Malky Mackay won't be too disappointed with his team as they were beaten by a very good side. However, the hosts may feel like they missed the opportunity to claim another surprising result in front of their supporters. Cardiff did not carry the same threat in attack as they did against Manchester United on Sunday and struggled to create opportunities during a good spell after the break.
Most of the time we're left talking about Arsenal's fluent passing and exciting attacking play but we saw a different side to Arsene Wenger's team today. Arsenal seem to be proving their critics wrong every week as they continue their impressive form. They were short of their best today but the visitors battled like champions to secure the result.
Sports Mole's man of the match
Aaron Ramsey: Who else could it be today? The Welsh midfielder is proving that it is not just a patch of form at the start of the season as his incredible campaign continued at the home of his former club. Ramsey's passing was as accurate as always, but it will be his two fine goals that will dominate the back pages tomorrow. Cardiff fans were singing his name in stoppage time, which tells you just how good he was today.
It's fair to say that Olivier Giroud did not have his best game this afternoon. Often playing a supporting role this afternoon, he had a chance to score in the first half but his hesitation while checking to see if he was in an offside position cost him as Cardiff recovered to clear.
Lee Mason enjoyed a routine day at the office as he made the correct decisions throughout the match and allowed the game to flow at a good pace.
Cardiff: Mackay takes his team to Stoke City on Wednesday evening as they look to recover from this defeat.
Arsenal: The league leaders are also in action on Wednesday as they take on Hull City at the Emirates Stadium.