Well, there IS an apostrophe...but no.
(Also, what is that? A frosted book?)
Not that letter.
("Nappy Boos's Day"? With a period? Seriously? Maybe this is a lost cause...)A-HA!! YES! You spelled it ri...oh. Wait. No, you're still wrong here. See, the plural of "boss" is just "bosses."
[rubbing temples with eyes closed] Um. Ok. Look. Yes, you did spell the plural of "boss" right, but "Boss's Day" is possessive. Plus you spelled "you're" wrong.
Now, "possessive" means that...[blinking]...ah, screw it. Can you just write the word "boss" so it's not plural OR possessive?
And you still spelled "you're" wrong.
[sigh] Alright, look, you want to see the perfect cake to get your boss? Something that gets right to the heart of the matter? Something spelled correctly, and conveying just the right amount of gratitude?
Note from John: It's true, some people accept "Bosses Day" as correct. However, considering this is a day for either your boss or your bosses, it really should be Boss's Day or Bosses' Day. Of course, the original singular possessive of boss was Boss', but I think that hurt our American brains so we added the extra s. Just make sure you never use Bosseses' Day and you should be fine.