This is the remote that should have shipped with the Fire TV Cube. Amazon recently announced a new remote that supports power and volume on Fire TV Cube.
This way you can now control your TV’s power and volume using your Alexa Voice Remote. This comes in handy as our experience with using the Fire TV Cube has been mixed. There are times when voice commands work flawlessly but times where it doesn’t hear or react to the action word.
If you order the Fire TV Cube now, Amazon will now send the new generation Alexa Voice Remote which has the power button. But if you are like me who ordered the Fire TV Cube early, you will need to buy the new remote which is now available for $29.99..
Amazon also has a page dedicated to help you set up your Alexa Voice Remote – https://www.amazon.com/gp/help/customer/display.html?nodeId=G47P2QLV6DKLKA6P