Preheat the oven to 425°F. Place 3 tablespoons oil in a shallow baking dish. Add the fennel, evenly coated in oil. Zest one orange and one lime over fennel wedges, Season with salt, pepper. Roast until caramelized, 30-35 minutes, turning halfway through. Remove from oven and reduce heat to 275°F.
While fennel is roasting prepare the cod. Cut fish into 4 even sized filets. Zest one orange and one lime over fish then. Season fish with salt, pepper and Aleppo pepper.
Slice 2 oranges and one lime into ¼ inch slices. Haphazardly place fish and citrus slices atop the fennel. Scatter serrano chili slices and add remaining olive oil. Roast until the fish is just opaque throughout, 25 to 30 minutes, depending on thickness.
While the fish roasts, remove the pith and peel from the remaining orange. Working over a bowl, segment the flesh, reserving any juices.
In a small bowl add 1 tablespoon of vinegar and a pinch of salt to the sliced shallots. Allow them to soften 15-20, then drain liquid.
Combine orange segments, olives and herbs in a small bowl loosely combine. When fish is removed from the oven, and just before serving, add a small amount of the flavored oil and reserved orange juice to the mixture. Season with salt and pepper.
Dollop the orange-herb relish and a small pile of the shallots over each piece of fish. To finish, squeeze additional lime, a sprinkle of dill, and flaky sea salt. Be sure to plate each fish with a piece of fennel and a drizzle of the flavored oil!