Place the first 6 ingredients in a small food processor, or in the cup that came with your hand blender. Puree until smooth. Spoon this chimichurri mayo into a bowl and refrigerate until needed.
Preheat the oven to 425 degrees F. Cut 2, 12” pieces of foil. Stack and wrap 4 tortillas in each piece of foil.
Place the fish in a single layer on a parchment paper-lined baking sheet. Drizzle with the oil and juice; sprinkle with Cajun spice. Bake 5 minutes, and then set the foil packages of tortillas in the oven. Bake 5 to 7 minutes more, or until the fish is cooked through and the tortillas are warm.
Set 2 tortilla shells on each of 4 plates. Divide and set fish in a row down the centre of each tortilla. Let diners top their tacos with chimichurri mayo and cabbage, to taste.
Note: Cajun spice is available in the bottled herb and spice aisle. Corn tortillas are available in bags in the dairy/cheese display case.