Combine everything but cod in bowl and mix. Set aside.
Bring 6 cups of water to a boil in a large saucepan, then gently lower the cod into the water (one fillet at a time) and bring the water back to a boil.
Reduce the heat to low and poach the fillets in barely simmering water for 3-4 minutes (they will be just cooked through).
Using a slotted spoon, lift the fish from the pan, drain, and place one fillet on each of 6 warmed dinner plates. Gently press the fish with a spatula or fork in order to make it separate just a little on the grain of the fillet.
Add 2 T of the hot poaching liquid to the lemon juice mixture, slightly beat and spoon the sauce over the fillets. Serve.