Preheat oven to 350°F (175°C). Grease and flour two or three 9-inch round cake pans.
Mix dry ingredients: In a large bowl, whisk flour, sugar, baking soda, cinnamon, and salt.
Add wet ingredients: Beat in eggs, oil, and vanilla until combined. Fold in mashed bananas, pineapple (with juice), and pecans.
Bake: Divide batter evenly between pans. Bake for 30–35 minutes or until a toothpick comes out clean. Cool in pans for 10 minutes, then transfer to a wire rack.
Beat cream cheese and butter until smooth. Gradually add powdered sugar and vanilla, beating until fluffy.
Layer cakes with frosting between each layer. Frost the top and sides.
Garnish with chopped pecans. Refrigerate for 1 hour before serving.