First, cut the pineapple in half lengthwise and core out the the fruit, leaving the pineapple shape intact. You'll use it later to serve out of.
Next, juice your limes. You'll need 1/4 -1/2 cup.
Dice your onions and garlic. Put in a bowl and top with 1/4 cup of lime juice. Let it sit while you work on the pineapple and cilantro. The lime juice will add flavour to the garlic and onion.
Chop the cilantro and dice up the pineapple.
Mix in the cilantro, pineapple and black beans in with the onion and garlic mix.
Taste - add more lime juice if you need it.
Eat it up.