Rinse the cod in cold water and remove any bones. Pat fish dry with a paper towel.
Rinse parsley and dry it before chopping the leaves. Set aside. Slice up the garlic.
If using fresh tomatoes, rinse, core, and peel them (optional). Cut the tomatoes into 1-inch wedges and remove the seeds. (If using canned tomatoes, just use four tomatoes from the can. Drain the juice and break the tomatoes into pieces with your hands.)
Heat a large, non-stick skillet on medium high. Add the cod and top with tomatoes, garlic, 2 tablespoons of parsley, pepper, and 1/4 teaspoon salt. Pour olive oil on top and bring the pan to a boil.
When boiling, put the heat on low and cover the pan. Cook until the cod can be flaked with a fork. The cooking time will depend on the thickness of your fish, but start checking after 10 minutes of being covered. Do not flip the fish.
When the cod is just about done, add olives for the last minute of cooking. Garnish with a tablespoon of parsley and add any extra salt needed before serving.