0I'm not sure whether native speakers refer to a bride and bridegroom as newlyweds during the ceremony. I usually hear it used after. So, I would say02br 02br 00The (or if you are a passerby - A) bride and bridegroom are cutting the cake together.0-
0At the time of the cutting of the cake, the couple are already married (perhaps already well on the way to divorce); so "newly-weds" would be possible.02br 02br 00I myself would use a plural verb, i.e.02br 02br 001. A pair of newly-weds are cutting the cake.02br 02br 00But other members would probably prefer "is"!02br 02br