1. Preheat oven to 275 degrees Fahrenheit. Coat the salmon with oil and season with salt and pepper.
2. Spread half of the blood orange, orange and lemon slices into a shallow baking dish and place salmon on top. Arrange the rest of the citrus over the salmon.
3. Roast salmon until it’s just cooked through (the tip of a knife will slide through easily and flesh will be slightly opaque), 30–40 minutes for medium-rare.