In a blender or food processor combine the oil, basil, parsley, garlic, lemon juice, and salt. Puree until the garlic is minced.
In a Ziplock bag or deep baking dish, add cod and asparagus. Pour marinade on top and make sure everything is evenly coated. Refrigerate for 10 minutes.
Transfer the cod and asparagus to a rimmed baking sheet with the fish lined down the middle of the tray. Arrange the asparagus on the sides.
Add the lemon slices and pepper to the top of the fish.
Cook for 7-10 minutes. The fish should be opaque and flake easily with a fork when done.
Serve immediately. Garnish with lemon slices and fresh parsley, if desired.
Notes
Probably nothing. Cod is naturally bland in flavor, which is why we marinate it before cooking. If you find your dish has little flavor, season liberally with salt and pepper, then spritz over some more lemon juice. Next time you make this recipe, you can leave it in the marinade for a little longer.