Mix together mayonnaise and sriracha to make spicy mayonnaise.
Add drained tuna to spicy mayonnaise. Mix thoroughly.
Heat pan on medium-high heat for a 1 or 2 minutes. In hot, oiled skillet place half the tuna mixture. After about a minute put cheese slices on top. Switch to medium to medium-low heat.
Splash a bit of water on pan to generate steam and cover the tuna and cheese to melt. While cheese melts, peel and slice avocado slices. Place avocado on one slice of bread.
Once cheese melts turn of heat and then transfer tuna and cheese mixture onto avocado bread with two spatulas. One spatula will slide under tuna and one will hold tuna on the side to stop it from sliding around. Cover with other slice of bread.
On medium heat, heat up pan with oil or butter. Quickly pan fry sandwich on both sides until golden brown. About 1 minute on each side.
Another sandwich can be made with remaining ingredients.
Serve immediately with something refreshing!
Enjoy!