To do it in DNS you'll need to have a dedicated IP# for the site, and both domains pointing to the same IP#.
You can do it using shared IP#s from the user control panel, but you'll have tradeoffs as to what appears in the browser window.
For example, type "http://www.nobaloney.com/" into your browser and notice how it changes to "http://www.nobaloney.net/". That's done from the control panel.
Jeff