It's a bird's nest fungus. See link below for more info.

Here is a link that might be useful: bird's nest fungus

OK, OK, I'll say it - there's a fungus among us. Looks to me like some sort of mycological growth.

They look like empty cupcake cups.

So do you think I can just uproot them? Or am I going to release spores into my house?

Pull 'em up and discard them. Completely harmless. No spores, to my knowledge. Those black things are "seeds".

Nancy

Not seeds, Nancy. Like just about all fungi, this one reproduces via spores.

The link which seedmoney posted is quite an interesting read, btw.

I have them growing on my land and some other oddities too. Fungus is weird.