Do you think it's weird that I only recently learned that hash browns contain onion?
I  don't think it's weird, but why did you just now learn about that?
I'm trying to eliminate onion from my diet, and wanted to check.
Sometimes when we have been eating a food our whole life, we just know that we enjoy it, not necessarily what's in it. It is okay to not know everything, as long as you are staying within your dietary restrictions.
I just can't believe I never thought about it before.
It's not that unusual to not know exactly what's in different foods. There's no shame in just finding out now.