Preheat oven to 350 degrees. Fill three cupcake pans with cupcake liners. (If u only have two cupcake pans, just use the two and chill the leftover batter until the others bake, then use the pan).
Mix flour, sugar, soda, salt and cinnamon in a large bowl.
In another bowl, mix together the eggs and oil and vanilla.
Pour the egg mixture into the dry mixture and mix with a spoon.
Add in the pineapple and mashed bananas and mix with a spoon. Add in nuts if desired.
Spoon two tablespoons of cake batter into cupcake liners (about halfway full). Add in a scant tablespoon of the filling on top of each cupcake.
Bake at 350 degrees for 20 min.
This recipe makes 36 cupcakes which is three cupcake pans. If you only have two cupcake pans, Chill any remaining batter and use it as soon as the other cupcakes bake and cool enough to remove from the cupcake pan.
Cool completely before adding cream cheese buttercream.
The tops of cupcakes will flatten out a bit while cooling because of the filling, but that's to be expected. You're about to pipe on some buttercream so don't worry.