Warm-up dungeons in Zelda are always great. Nintendo knows how to tutorial.
First dungeon in Zelda 1 is excellent. Throws in a wide variety of enemies, introduces the concept of wall bombing even if it’s completely unnecessary there, and puts the item at the end of a side road so you understand that you can’t just go straight to the boss. The boss is also fair, but not really a pushover.
But maybe my favorite is Tail Cave from Link’s Awakening. Giving you the ability to jump in the first dungeon speeds up the game and makes traversal quicker right from the beginning. Good boss and miniboss, too. It’s an incredibly satisfying level through and through.