Cut a piece of foil three times the length of each cod filet. Arrange half the ginger, cilantro, and scallions on the center of the foil, and place the cod fillet on top. Mix the kosher salt and lime zest together and sprinkle on top of each filet. Fold the long part of the foil over the cod and roll edges to make a sort of tent/envelope. Place the foil on desired steam cooker, over medium heat, and steam approximately 6-8 minutes.
Place the green bell peppers, poblano peppers, and tomatillos on a small sheer pan and under the broiler it goes to char. Remove from the oven to cool. Peel and seed the peppers and tomatillos. In a food processor, pulse the nuts medium/ fine. Pour the crumbled nuts into a bowl and set aside. Add the peppers, garlic, tomatillo, Sherry vinegar, and olive oil to the processor. Process until pureed smooth. Add the nuts and herbs to the puree and pulse until combined. Taste for seasoning. Carefully unwrap the foil and remove the cod with ginger and scallions to a plate. Top with a spoonful of the Romesco sauce.