Peel the bananas and fill up a large casserole with water and some salt.
Put the bananas in the water and boil for about 20 minutes, or until the bananas are soft enough for you to insert a fork, but not so soft that the bananas fall apart. Check after 15 minutes for this, just in case.
While the bananas are boiling, combine the sliced onions, olive oil, vinegar, bay leaves, black pepper corns, garlic, salad olives, and “adobo” or salt, in a small medium saucepan.
Leave them at a medium/low heat so that the mixture warms up but does not boil, for about 10- 15 minutes. You want it to be warm and the onions softened a bit.
If you use the full cup of white vinegar, the taste will be tangier and brinier. I like the tangy flavor, but if you are not sure, start with a ½ cup of vinegar and add more after you taste it, if you like.
When the bananas are done boiling, carefully drain them and cut them up into ½ inch pieces.
Place them in a glass bowl and pour the warmed-up "escabeche" over them.
Leave them in the fridge preferably overnight. The more time you leave them marinating, the better it will taste.
Serve at room temperature as an appetizer or accompaniment