Heat the oven to 325 degrees. Place the salmon in a shallow baking dish that fits it with at least 1 inch around all sides. Rub the fillet on the top and bottom with some olive oil then season with salt and pepper.
In a large bowl, combine 2 tablespoons olive oil, the radicchio leaves, olives and chile flakes. Season with salt and pepper and toss to coat evenly. Scatter the mixture over the salmon, letting any leaves and olives that fall onto the baking dish stay there.
Bake until the salmon is opaque on the outside and an instant-read thermometer inserted into the thickest part of the fillet reads 120 degrees for medium doneness, 30 to 45 minutes depending on the thickness of the fillet (if you want your salmon just cooked through, take it to 130 degrees).
Remove the pan from the oven and squeeze the juice of the lemon all over the top of the radicchio and salmon. Let the fillet rest for 5 minutes then serve family-style, straight from the baking dish with the side of your choice.
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