Where did you find it? What size is it? And where are you?

It looks more like a bug egg than a plant seed. Elephant Hawk Moth might be it, but there are a couple other critters with somewhat similar eggs. If it is the Moth, those are beneficial pollenators.

I agree w/beesneed.

That being said and FWIW, the only seeds I'm aware of that look remotely like this are those of the Amaryllidaceae, but particularly the Amaryllidoideae subfamily.

gooseberry? (slightly fermented).

I'm wondering if it's an oak currant gall. https://rcannon992.com/2022/06/13/oak-galls-currants-and-spangles/

Definitely not a gooseberry.

More information would really help. Location? Nearby trees or plants? Size?

That's a great suggestion floral.

I've never seen those before.

That is a great suggestion! I'm not sure I've seen that before. Or maybe not paid enough attention. Seen a few other kinds of galls.

Here all this time I thought my bur oak had every imaginable kind of gall there was.

Live and learn. ;-)

I haven't checked if you get these galls in the US.

With little idea of scale, I have to say it looks exactly like a whitecurrant (mine, at any rate) currently (ha) at this exact stage of development.