Pour 3/4 cup water in the pot. Place the fish in a steamer basket and season with coriander, parsley, salt, smoked paprika and pepper.
Lower the steamer basket into the pot, then secure the lid, making sure the vent is closed.
Using the display panel select the MANUAL or PRESSURE COOK function*. Use the +/- keys and program the Instant Pot for 2 minutes.
Meanwhile, in a medium bowl, combine the Topping Mixture ingredients and toss to coat.
When the time is up, quick-release the pressure. Check the fish for doneness. If fish is not quite done, simply close the pot for a few minutes and allow residual heat to bring to desired doneness.
Serve the fish in tortillas with the cucumber relish, cilantro, sour cream and lime wedges.