Lightly butter one side of each piece of bread. Pan fry one piece in a skillet over medium heat.
Make a quick tuna salad mixture by combining the tuna with mayonnaise or yogurt, garlic, dulse, salt and pepper. Spread over the first pieces of bread. Top with slices of avocado and then cover with a slice of cheese. Place the remaining bread on top. Press down and once the bottom piece is melted, flip and cook the second side until the cheese is melted.
Serve warm, slice in half if desired.
For an open faced sandwich: prepare the sandwiches in the same way. Leave off the second piece of bread. Cook the sandwiches until the bottom is golden. Turn the oven broiler on high, place the sandwiches on a baking sheet and put in the oven. Broil for 2 minutes or until cheese is melted and bubbling. Remove from the baking sheet and serve warm.
Note on the avo: I fit 1/4 of an avocado on each sandwich then divide the remaining 1/2 of avocado on the serving plate.