World Optimus Prime other death

I remember, when I was a kid (of course), I saw an animated show of Transformers when Prime dies on Cybertron (I suppose). He went in a dome building and sacrificed himself (don't remember why) and he died when the dome exploded.
My doubt is if this is a real episode or, maybe, a fake created by my mind... you know, like when you remember a movie scene, but when you watch it again after many years you don't find it.

 

Thanks! I've also made a search on youtube.com and I've found that. It looks like an homage to the death in the movie. I've also found another death in season 3. But both are quite different from what I remember. Strange thing, our mind.