If your Apple TV model is the 2012/2013 3rd generation model [A1427 or A1469], with the old style Apple Remote (aluminum) [A1294], then controlling the TV is not supported, nor is CEC supported.
If your Apple TV is of a later model [A1625 or later], then CEC would be supported.
If you Apple TV is the 2021 model 4K 2rd generation or later [A2169 or later], then CEC would be supported, and also the Siri Remote (2nd generation or later) would have a power button.
Identify your Apple TV model - Apple Support
Find your Apple TV model number - Apple Support
Identify your Apple TV remote (with compatibility listing) - Apple Support
To make the Apple TV box wake both itself and the TV from standby, verify that the TV supports Power-On by CEC, and has CEC activated. Also set Apple TV to activate CEC.
On Apple TV: Settings﹥Remotes and Devices﹥Control TVs and Receivers﹥On
On your TV: See its manual.
To wake the Apple TV box and HDMI-CEC supported equipment in the setup, use the Menu or Back button or alternatively the Power button (if present).
Consumer Electronics Control (CEC) - Wikipedia