Preheat your oven to 350°F (175°C). Grease and flour a 10-inch bundt pan very well. This will help the cake release cleanly after baking. You can also use baking spray that contains flour.
In a large bowl, whisk together the flour, sugar, baking soda, cinnamon, and salt. Make sure everything is well combined to ensure even distribution of the leavening agents and spices.
Add the vegetable oil, eggs, and vanilla extract to the dry ingredients. Mix until just combined. Be careful not to overmix, as this can make the cake tough.
Gently fold in the mashed bananas, crushed pineapple (with its juice), and chopped pecans until everything is evenly distributed throughout the batter.
Pour the batter into the prepared bundt pan, spreading it evenly.
Bake for 50-60 minutes, or until a wooden skewer inserted into the center comes out clean. Check for doneness around the 50-minute mark to avoid overbaking.
Let the cake cool in the pan for 10-15 minutes before inverting it onto a wire rack to cool completely. This prevents the cake from sticking to the pan.
If desired, frost the cooled cake with cream cheese frosting or dust with powdered sugar.