In a large bowl, roughly mash the bananas, avocados, lemon zest, lemon juice, honey, creme fraiche, and 2 teaspoons salt with a fork. Transfer the mixture to a food processor or blender. Puree the mixture until really smooth. Place the mousse in a clean bowl and put in the freezer for at least 1 hour before serving.
For the red onion puree: Heat the oil in a large saucepan until just smoking, then add the onions and cook until theyre deep brown. Stir constantly so the onions dont burn. When the onions are browned, add the red wine, port wine, and remaining 2 teaspoons salt, and simmer to reduce until the onions have absorbed all the wine. Remove the pan from the heat and transfer to a food processor or blender. Allow to cool for 1 minute. Puree the onions and run through a fine sieve and let cool.
To serve: In a martini glass, place a scoop of the mousse and top with the red onion puree. Enjoy as an appetizer or funky dessert.
This recipe was created by a contestant during a cooking competition. It has not been tested for home use.