Another solution is to dab a *tiny* bit of hot melt glue on the end of a needle, let it dry on the dome and then pull. I've fixed some badly crumbled titanium domes like this, but if you apply too much glue, you're in trouble.

As a last, last resort... When all else fails... You can poke a needle into the dome sideways and then pull it out. The tiny hole won't really effect the operation of the tweeter.

Adam