Heat a large griddle or nonstick skillet with cooking spray and set over medium-high heat. Season tomatoes with salt and black pepper and add to hot pan. Cook 1 minute per side, flipping with a spatula, until golden brown. Remove from heat.
In a small bowl, whisk together mayonnaise, basil, chives, mustard, and lemon zest. Spread mixture on rolls. Top with seared tomatoes, catfish, lettuce leaves, and red onion.