Superman: War of the Supermen #3

Synopsis

Superboy and friends defeat the general's team at Mount Rushmore, but Flamebird senses the problem with the sun turning red. She and Nightwing go to investigate, but The Nightwing entity tells Nightwing to stop, while Flamebird sacrifices herself to turn the sun normal again. Although many Kryptonians had perished in space while the sun was red, Superman and Supergirl recover, and go to Earth to fight Zod and company.