Preparation

1. To make the tomatillo salsa, preheat the broiler. Soak the chopped onion in iced water.
2. Place tomatillos (cut side down), peppers and garlic on a foil-lined broiler pan about 4 inches from the hot broiler for about 5 minutes or until blistered and blackened. Turn and char the other side, about 5 additional minutes. Allow to cool.
3. When cool, remove the heavily charred skin from the tomatillos and the stems, skin, and seeds from the peppers. Peel the garlic. Combine the tomatillos, the peppers, and garlic in a food processor or blender. Process to a coarse puree.
4. Transfer to a serving bowl. Drain the onions and fold into the puree along with the cilantro. Taste and adjust seasonings with salt and pepper.
5. Preheat the broiler. Re-use or reline the broiler pan with foil.
6. Squeeze the juice of one of the lemons over the fish and pat dry with paper towels. Place fish onto a large platter and rub with the olive oil. Sprinkle the top side of the fish with the rub and arrange in a single layer on the prepared broiler pan while you prepare the rest of the meal.
7. Place fish about 4 inches from the broiler and cook approximately 10 minutes, no need to turn. If broiler is too hot and flare-ups occur, change oven to 500 F and cook for the full 10 minutes or until the flesh in not translucent when parted.
8. The rule of thumb for cooking fish is to allow 10 minutes per inch, judging from the thickest part of the fish. Do not overcook or the fish will be dry and boring.
9. Top each fillet with tomatillo salsa and serve.