My own tuna melts that my kids love!
Substituting Greek yogurt for the mayonnaise alters both the moisture balance and the protein structure of the salad, requiring careful monitoring of the celery and onion ratios to prevent excess liquid pooling on the bread. Uniform dicing of the vegetables to a quarter-inch size ensures that every bite distributes the crunch evenly throughout the denser tuna protein.
Scaling quantities upward requires maintaining strict proportions of mustard and pickles, because doubling acid levels alters the emulsion stability when combined with dairy fats during heating. Batch cooking necessitates using standard rimmed baking sheets lined with parchment paper to catch any melting provolone before it burns against the metal surface.
Baking at 350 degrees Fahrenheit for 12 minutes provides sufficient thermal energy to warm the tuna through without overcooking the fish or making the mayonnaise separate into an oily residue. Visual doneness occurs when the cheese margins turn light golden brown and bubble gently across the surface.
Over-saturating the bread with un-drained tuna remains the primary error leading to structural failure under the broiler heat. Pressing the canned tuna against a fine-mesh strainer removes excess packing water before mixing.