Set the oven rack to middle position and heat oven to 350°F. Lightly spray cake pans with nonstick baking spray and line with parchment paper. Spray the parchment paper with nonstick baking spray.
Drain the pineapple in a fine-mesh strainer set over to bowl to catch the drippings. Press the pineapple with a rubber spatula to extract as much juice as possible. Set a small saucepan over medium heat and add the pineapple juice. Cook until reduced to 1/3 cup, 6-8 minutes; set aside to cool.
While the juice reduces, place the pecans on a large baking sheet and place in the preheated oven, on the middle rack. Toast the pecans until darker in color and fragrant, about 6-8 minutes. Watch closely after the 5 minutes mark – pecans burn easily. Remove the pecans from the oven and pour them onto a large plate to cool.
In a large mixing bowl, whisk together flour, baking powder, baking soda, cinnamon, and salt.
In a separate large mixing bowl, whisk together sugar and eggs until incorporated. Continue whisking while adding the oil. Stir in bananas, toasted pecans, vanilla, drained pineapple and the cooled reduced pineapple juice.
Add the flour mixture and mix just until no flour is visible.
Pour the batter, evenly, between the prepared pans and smooth the tops.
Bake at 350°F until dark golden brown for 25-40 minutes (depending on the pan size), or until a toothpick inserted in the middle comes out clean. Rotate the pans halfway through baking.
Transfer the cakes to a cooling rack to cool (in the pan) for 20 minutes.
After 20 minutes, remove the cakes from the pans, discard the parchment, and let cool completely on the cooling rack.