Banana cake

you can use turbinado sugar on top of fresh banana and use a culinary torch to just caramelize the top of the bananas, they look really pretty that way. My favorite filling with banana cake is marscapone frosting.

Also, both the jam and the compote sound amazing. Any tried and true recipes you'd like to pass along?

I'm fine with a caramel-brown (I.e) like a bananas foster. What I don't want it that's kind of Greyish color that comes with spiced raw bananas. I would be cooking the banana in a brown sugar syrup.

Cooked bananas tend to be more brownish than black. I recently made banana jam and it looks like caramel: golden brown. I don't have a problem with this. But if you want something more appealing in appearance, maybe you could mix the sauteed bananas into a buttercream frosting, some sort of pastry cream or make a curd with banana. Pictures of banana cake filling that I've seen online aren't black or brown at all.

Are you doing something "banana's foster-y" or do you just want to caramelize bananas on the outside? I've made a brown sugar, brown butter, banana, cinnamon compote and cooled it to fill a cake. It didn't blacken, but it was definitely an earthy brown color. I didn't find it unappetizing, but if you're looking for banana yellow, you'd be disappointed.

Simply sautéed bananas, though, I'm afraid would probably oxidize. Even when I make banana cream pie, the bananas inside oxidize a little. If I'm working with bananas, I'm making sure always that I'm making the dessert as close to serving as possible.