Who says it is a no-no to lead an Ace against a No Trump contract!
There are always exceptions and many guidelines in this fabulous world of bridge.
Certainly with AKQ2, AKJT (3-card sequences or broken sequences) we certainly do it.
However, when we hold AK43 without unsupporting honors we will lead the King for fear of giving declarer the Queen.
We ask for an attitude signal from partner on this lead.
We also retain the lead, so when we see the dummy, we can judge whether to abandon the suit, and guide us to a better line of defense, by switching to a more promising line of play.