Preheat oven to 400 degrees F.
Clean the bass by removing the guts and the gills and trimming off the belly flap. Season the season with salt and pepper. Place the fish on foil and sprinkle with some citrus zest. Close the foil and cook for about 10 minutes oven. In a small sauce pot reduce the juice and the remaining zest. Slowly add the butter whisking constantly, season sauce and add all the segments, simmer. Saute the spinach and drain off any liquid. Remove the bass from the oven and from the foil, discard the citrus zest on it. Place the fish on top the spinach and ladle with the citrus sauce