Onions: Thinly slice the onions, and place in a non-reactive dish. Combine the remaining ingredients and bring to a boil. Pour over onions and let stand for 24 hours.
Fondue: Preheat the oven to 300 degrees F.
Cook the bacon until crispy and fat is rendered. Reserve the bacon and the fat separately. Combine the tomatoes, garlic, 2 ounces of the reserved bacon fat. Roast until the tomatoes are almost dry. Place in the blender, add the goat cheese and puree. Strain through a fine chinois and reserve.
Yellow Tomato Coulis: Quarter the yellow tomato. Coat with olive oil, salt, and pepper and roast for 20 minutes. Remove and puree in a food processor. Season with salt, pepper, and lemon juice. to taste. Reserve Malanga Tumbleweed: Peel malanga and cut into thin ribbons on a turning slicer. Preheat a deep fryer or a deep pot of oil to 350 degrees F. Fry the malanga until crisp and remove to a paper towel-lined plate. Reserve.
Basil Oil: Blanch and shock the basil. Wring out in a clean, dry towel. Place in a blender with oil and puree for 1 minute. Let stand for 1 hour and strain. Reserve.
Season the fish with salt and pepper and lightly dust with flour. Saute, skin side-down, in a very hot pan until skin is crispy. Turn the fish over and finish in the oven.
Place pickled onions in the center of a plate. Rest 1 piece of fish across the onions, allowing them to peek out. Drizzle with the fondue, coulis, and basil oil. Sprinkle the bacon around the fish and top with fried malanga.