For the fish: In a bowl, combine the oil, spices, salt and pepper. Add the fish and make sure each piece is coated with the marinade.
For the mayo: Put the mayonnaise, garlic, mint, cumin, and lime juice in a food processor. Whizz until smooth. Season with salt, pepper, and more lime juice, if necessary. Pour into a bowl and set aside.
Grab a large, nonstick saute pan and warm it gently over medium heat; no need to add oil since the fish is already coated in oil. Once warm (test by sprinkling some water into the pan, if it sizzles and evaporates, you're ready), place each piece of fish in the pan. It should sizzle gently but firmly when it hits the pan. Cook until cooked through, but still moist, about 3 minutes per side. The fish should flake easily with a fork. Don't overcook your fish! It'll taste awful!
Remove the fish from the pan and serve immediately with warmed tortillas. I put a light layer of cabbage on the bottom, then the sauce, a few chunks of fish, the scallions, a couple of slices of banana pepper, and a squeeze of lime. And once the fish is finished off, you can do what I do, and make cabbage tacos - everything except the fish! So good!
Christina Perozzi from beerforchicks.com suggests an Allagash White from Portland, Maine. It's an ale brewed with coriander and bitter orange peel which works perfectly with the tacos, harmonizing with the spices and also providing herbaceousness and citrus!