My friend is looking for a cartoon about a boy and a robot in a red cape (the robot itself is not red, it is dressed in a red cape). The action takes place in the desert, where they were preparing for some kind of battle. The cartoon was 3d. A friend saw it in 2006-2008, but does not remember on which channel
Eon Kid (IMDb, Wikipedia) (or Iron kid) has a robot in a red cape Gaff, who is the robot guardian of the Eon family, and in particular Marty, the protagonist. Marty wears and wields an Iron Fist, an heirloom of his family, and goes on a quest to destroy the tyrannical robot General. When wielding the fist, he can equip his ancestor's armour, giving him superhuman abilities.
It fits the time scale well, first airing in the US in 2007.
Found with google search
3d cartoon robot desert boy