So it's not "a tax that a country imposes on goods entering its borders" now?
If you trade oil with cuba, then any trade with the US will be subject to the tariff.
I'm not sure what in my comment you think contradicts this.
I can see how this wording makes it sound like the US is charging a tariff on the oil entering Cuba, but that is not the case. The tariff in that quote is referring to the tariffs the US is promising to place on counties that don't participate in the embargo.