Puzzled: Two Move Checkmate

I've been struggling with this puzzle on my phone for awhile now.  It's white to move and checkmate in two moves.  I feel like I've tried every possibility and don't know how to solve this.  

If someone knows how to solve this please show me!  Thanks!

Oh yeah that worked. Brilliant! Cheers for that!

I was beginning to think it wasn't really solvable.

c8=Q+  Nxc8

Qxc8#

 knight has vacated a7 so

...Ka7

Good puzzle, Sallen.

Was reduced to trying every possible move.

And a "well done" to EarlPurple.

Qb8+ Ka6 or Kc6

Q b6#

No balfer -- Kc6, Q b6 not mate because of Kxd7.

I don't believe it is mate in 2 at all.  Best is mate in 3.

It's mate in 2. It's from 2011 when people still posted decent problems 

So what is the solution?  I cannot see it!

Hint number one...The first move is a diagonal queen move.

1. Qa2

Is that hint number two?

You're right!  This is an excellent puzzle.  Interesting that the analysis icon did not suggest this move since it usually goes for the quickest mates.

It very often fails miserably in interesting positions. It's probably true that it rarely goes for quickest mates.

The Syzygy EGTB (https://syzygy-tables.info/?fen=N5Q1/nkPP4/8/8/4K3/8/8/8_w_-_-_0_1), which plays perfect (if not perfectly accurate) chess with this number of men puts c8 or d8 equal first (irrespective of the promotion piece).

Moral: trust yourself.

Syzygy favors zeroing over mating. It's a lifestyle

I know why it does it. I was just pointing out it's probably not the best method of solving mates in two.

Actually firstly it is about pinning knight to king with zugzwang, and then promoting.

By the way, solved it.

Actually, Syzygy behaviour is covered by my broader theory on retrograde logic. If you know absolutely nothing about the past then Syzygy's choice is superior to the formal #2 solution. And the same is true for almost every #2 since their key moves are mostly not pawn moves or captures. However the current (retro-) conventions do not cover this issue properly which makes Syzygy's choice a reminder of one of the many things flawed in these supplementary decision rules!

But here you do know something about the past. According to the FEN the previous move was a capture.

(According to the FEN all castling rights are also in effect, so the position could not have been arrived at by a legal series of moves from the starting position. Presumably it's OK to castle so long as you can find a king and rook in their starting positions but if either king moves the corresponding rights disappear.)