In a small bowl combine all of the spices and mix well.
Using 1 tablespoon of olive oil, brush the fillets and then rub them with the spice mixture. You will use the entire rub – so make sure to coat them very well.
Refrigerate the cod fillets for at least 30 minutes, or up to 12 hours.
Preheat the oven to 450º.
Place the cod fillets on a foil-lined baking sheet and roast in the oven for 10-12 minutes; the fish will flake easily and be opaque throughout when it’s cooked through.
Meanwhile in a small sauce pot, melt the butter with the remaining tablespoon of olive oil. Add in the lime zest and juice and swirl the pan to mix.
Serve the cod over the top of rice and Mexican corn, if desired, and top with the lime butter.