I need a good recipe and I have a question. I have nver done this before. Can I fill a cake with banana cream filling and cover in fondont? Does it need refrigeration? Or how long can it sit out before bananas go brown? I am so nervous this might happen.

Banana filling that contains bananas is only good for about 24 hours and does require refrigeration.

Here is an easy banana cream filling. The maceration helps extend the life of the bananas to 1 day instead of a few hours.

1 4 serving size package banana or vanilla instant pudding mix
1 cup whole milk or evaporated milk
2 cups heavy cream, whipped OR 2 cups Cool Whip (regular)
2 large just ripe (all yellow, very little or no brown, no green) bananas, sliced into 1/4" thick slices
2 tbsp sugar
1/2 cup lemon juice

Dissolve the sugar in the lemon juice and then pour into a gallon sized zip top bag.
Add the sliced bananas, gently squeeze all the air out of the bag without smooshing the bananas and seal the bag.
Place bag in refrigerator for 30 minutes.
Meanwhile, mix the pudding mix and the milk until the pudding mix is dissolved and the mixture is thick and creamy.
Fold in the whipped cream or Cool Whip and refrigerate.
Drain the bananas and fold into the pudding mixture.
Store in fridge.
Good for 24 hours.