How to Make It
Season halibut fillet evenly with 3/4 teaspoon of the salt and 1/4 teaspoon of the black pepper. Heat 2 tablespoons of the oil in a cast-iron skillet over high. Add fillet; cook, undisturbed, until deeply browned and a thermometer inserted in thickest portion of fillet registers 140°F, about 6 minutes per side. Remove fillet from skillet; let rest 5 to 10 minutes. Flake into 1-inch pieces.
While halibut rests, stir together lime juice, mayonnaise, and remaining 1 tablespoon oil, 1/4 teaspoon salt, and 1/4 teaspoon black pepper in a medium bowl. Add coleslaw, bell pepper, cilantro, and scallions; toss to fully coat.
Spoon about 1/4 cup slaw mixture onto each of 8 warm tortillas; top evenly with flaked halibut. Top each taco with 1/2 tablespoon pico de gallo and 1 teaspoon queso fresco.