Preheat a grill pan over medium-high heat.
Season the catfish on both sides with 1 tablespoon Cajun seasoning, salt, and pepper. Brush the grill pan with some of the canola oil and grill the catfish until cooked through, 4 to 5 minutes on each side. Remove to a plate and let cool.
Into a large bowl, add the cracker crumbs, 2 tablespoons mayonnaise, mustard, and egg. Shred the fish with a fork and add to the bowl. Fold everything together. Form into 8 small cakes and set them aside.
In a large skillet over medium heat, add the remaining canola oil. When it is hot, add the catfish cakes and cook until browned on each side, 4 to 5 minutes total. Drain on brown paper.
While the cakes are cooking, make the remoulade: In a bowl, stir together the remaining 1 cup mayonnaise, 1 teaspoon Cajun seasoning, 1 teaspoon mustard, hot sauce, lemon juice, and garlic. (Reserve 1/2 cup remoulade for Round 2 Recipe Cajun Quesadillas.)
Serve the catfish cakes with the remoulade.