How to Make It
Using a paring knife, cut a slit down the side of each chile. Open each chile, and remove and discard veins and seeds. Heat a large comal or cast-iron skillet over medium. Add chiles, and cook until fragrant and chiles begin to darken, about 30 seconds per side. Remove chiles from pan; set aside.
Combine toasted chiles, onion, vinegar, cumin seeds, salt, peppercorns, garlic, and cloves in a blender, and puree until a smooth paste forms. If paste is too thick, add water to thin to desired consistency (I use about 6 tablespoons water to 1 cup adobo).
Preheat oven to 300°F. Season fish with salt. Spread 3/4 cup adobo over fish to completely coat fillets. Line a medium baking dish with parchment paper. Add fish, and drizzle with oil. Roast in preheated oven on middle rack until flesh is opaque throughout and flakes easily with a fork and a thermometer inserted in center of fillet registers 135°F, about 30 minutes. Let fish rest 10 minutes.
In the same blender, add tomatoes, salt, and 1/4 cup adobo. Process until smooth.
Toss together onion, radishes, lime juice, and oregano in a small bowl until combined. Season with salt to taste. Serve fish with onion mixture, avocado, salsa, and hot, fresh tortillas.