For the salsa:
For the fish:
To make the salsa, reserve a few tablespoons of the blood oranges. In a small bowl, combine the remaining blood oranges, onion, and cilantro. Squeeze the juice from the reserved pieces of orange into the bowl. Season to taste with salt and pepper. Add in the olive oil. Toss well to combine, taste, and adjust seasoning as necessary.
Preheat the oven to 425˚ F. In a small bowl, combine the butter, jalapeño, cilantro, salt and pepper. Stir well with a spoon until evenly combined. Pat the top of the fish dry and spread each portion with a thin layer of the butter. Coat the bottom of a large skillet with olive oil and place over medium-high heat. Add the fish to the pan, skin side down, and cook 3-4 minutes. Transfer the pan to the oven and let cook until the internal temperature reaches 145˚ F, about 8-12 minutes.
Remove the fish to a serving dish, separating from the skin as you do so. Let rest a few minutes, then top with the blood orange salsa and serve immediately.