Preheat the oven to 425ºF. Line a baking sheet with parchment paper.
Mix the chili powder, garlic powder, salt, and pepper in a small bowl. Season the fish with the spice mixture and place on the baking sheet. Scatter with jalapeño slices. Drizzle with olive oil and brush to evenly coat.
Bake until the fish is firm and opaque, about 12 minutes. Flake the fish into bite-sized pieces.
For the sauce, blend the mayonnaise, chipotles, pomegranate molasses (or honey), cilantro, and lime juice in a food processor or blender until smooth.
Serve the flaked fish in warmed tortillas with pico de gallo, shredded cabbage, a generous drizzle of sauce, and a squeeze of lime.
