In a medium bowl, combine fish, 2 tablespoons of olive oil, lime juice, chili powder, salt, garlic powder and pepper. Let stand 15 minutes.
While the fish is marinating, make the sauce: In a food processor, combine all ingredients and process until fully blended. Transfer to a squeeze bottle.
Heat remaining 2 tablespoons olive oil in a nonstick skillet over medium-high heat. Add fish and any marinade from the bowl. Cook fish about 4-5 minutes, stirring once or twice to ensure the fish is fully cooked through on each side.
Place corn tortillas between two damp paper towels and microwave for 30 seconds.
Assemble tacos by placing fish on top of tortillas, topping with salsa (if desired), cabbage and drizzle with chipotle sauce.