- Pat the seafood dry with a paper towel (if using shrimp or scallops, rinse and drain, then pat dry.) Season lightly with salt and pepper.
In the same pan used for the fennel, warm 1 to 2 teaspoons oil over high heat until hot but not smoking.
Halibut:
Add the halibut and cook until browned on one side, 2 to 3 minutes. Turn the halibut and add the fennel mixture, tomatoes, and 1 cup [2 cups] water; season with salt and pepper. Bring to a boil, then reduce to a simmer and cook until the halibut is opaque and flaky, 2 to 4 minutes. Remove from the heat.
Jumbo shrimp:
Add the fennel mixture, tomatoes, and 1 cup [2 cups] water; season with salt and pepper. Bring to a boil, then reduce to a simmer. Add the shrimp and cook until firm and cooked through, 3 to 4 minutes. Remove from the heat.
Scallops:
Add the scallops and cook without turning until golden brown on one side and starting to turn opaque, 2 to 4 minutes. Transfer the scallops to a plate. Add the fennel mixture, tomatoes, and 1 cup [2 cups] water to the pan; season with salt and pepper. Bring to a boil, then reduce to a simmer. Add the scallops, seared sides up, and cook to the desired doneness, about 30 seconds for translucent or 1 to 2 minutes for opaque. Remove from the heat.
To the pan with the seafood, stir in the sumac and season to taste with salt and pepper.