Drain tuna. In a medium bowl combine drained tuna with Greek yogurt, dijon mustard, lemon juice, corn, red onion, relish, garlic powder, and black pepper. Mix to combine.
Heat a burrito-sized wrap or tortilla to make it more pliable by covering it with a damp paper towel and microwaving it for about 10-20 seconds. Place it on a clean working space. Add a layer of shredded cheese on the end of the wrap closest to you, leaving at least an inch of space on the sides and bottom edge. Add the tuna mixture on top of the cheese.
To wrap, fold sides of tortilla toward the middle. Then fold the bottom of the tortilla and tuck the edges of the wrap under. Roll the tortilla away from you to the edge.
Heat a skillet or grill pan on medium heat and add a bit of olive oil. Place the wrap on the hot grill pan or skillet, seam side down. Let it heat for about 3 - 4 minutes, gently pressing on it a couple of times while it heats. Flip the wrap and heat another 2-3 minutes. If it's cooking too quickly, lower to medium-low heat.
Hint: Use a burrito sized wrap or tortilla! If you prefer, make it into 2 smaller wraps by dividing the tuna mixture between two smaller regular sized tortillas.