"Seo an t-ìm."
Translation:This is the butter.
It means (and I think your translation should be accepted). But notice how in this is the butter the word this might refer to just an abstract direction at which you’re pointing, not necessarily a physical object, in that sense the sentence is very close (if not identical) in meaning to here is the butter, you’re just pointing at something close to you to show someone where the butter is, which container has the butter in it, or something like that.
Both meaning (this is X, here is X) can be expressed in Gaelic by seo X.