Originally Posted by FBinNY

Sorry, but you can't adjust brake (or gear) cable tension. That's set by the brake's return spring.

You adjust cable length, and if you have it so the brake clears the disc when released, and can apply full braking power before the lever runs out of travel, then all is good. If you're having trouble getting both release and full power within the throw of the lever, then the problem may be cable compression, or play in some of the fittings.

Brakes vary in the strength of their return springs, and lighter spring are considered a plus because they make for a lighter action so all your hand strength is used braking rather than overcoming the spring.