Preheat oven to 350 degrees.
In a large frying pan, heat oil on medium.
Add onion, yam, fennel, and red bell pepper.
Season with salt and pepper, add crushed garlic.
Sauté lightly for 1–2 minutes (don’t overcook, salsa should remain crunchy).
Meanwhile, in a small frying pan, crisp the prosciutto or bacon. To the onion mixture, add tomato, ½ of the cilantro, ½ of the prosciutto or bacon, and chili flakes.
Stir to blend flavors.
Adjust seasoning.
Cut two pieces of aluminum foil into 12-inch squares.
Place a handful of spinach on each piece of foil.
Sprinkle with oil, lemon juice, salt, and pepper.
Place the filet on top.
Sprinkle with oil and lemon juice.
Top with a generous spoonful of salsa.
Garnish with remaining prosciutto and cilantro. Loosely close aluminum packet and bake for 10-15 minutes or until fish is done.