I know nothing on the subject, but just suspecting that it might be called a “death cap” would be enough to stop me from eating it

Sure looks like one to me, though it is paler than they usually are (edit: colour variation is perfectly normal for death caps though). It certainly isn't any edible species that I know of.

That being said mushrooms are somewhat local and I live on the other side of the world so take this identification with a grain of salt.

Show us the volva

It looks like the gills aren't attached which is a sign that it is but a cross section would help. Almost certain it is though, especially being under an oak. Bit late in the year yeah but california is temperate enough that its still entirely possible.

Spore print would help w/ ID, white is a (+) association. No staining/ bruising of cap and stip is (+). Also presence/ absence of a volvulus at the ground end a bulbus stipe/stem would be typical of the Amanita genus. The smooth stipe/stem is a (-). I've ID'd A. phaloides before in the field. This one would be high suspicion (+), and since it also doesn't look like anything I do forage, would be a 'pretty picture, learning experience', and let's keep looking.

It certainly does look like one. I'm just an armchair mushroom guy though.

https://www.mushroom-appreciation.com/destroying-angel.html

Western Destroying Angel, I will assume that one is also poisonous? Mycologists don't fuck around with their naming conventions do they?

Then you have Chicken of the Woods, and Lobster....

☠️ neat ☠️

Does it grow from a "cup" at the bottom? Then definitely