How have you been rascals? Long time..
Anyways, like a real Jew I only drop by because I need a favor.

I'm making this button for a website and I had a clear design in mind.
Problem is: I can't seem to translate it into gradients.

Here is the button:

The grey around the button should look like it's straight slope, rising up to the button.
(so if you were to push the button, the edge of slope around it would be higher)
Hard to explain, but I hope you catch my drift.

Instead, it looks somewhat "round" or bulging.

How do I make it look straight, rising up towards the center?