Strain the canned tuna, quickly, and then add to a bowl (you just want to strain most of the liquid off not all of it).
Add in 1 tablespoon finely diced shallot or red onion, 1 teaspoon fresh-squeezed lime juice, ½ teaspoon garlic powder, 1 teaspoon minced parsley or cilantro, and 2 dashes of cayenne pepper (optional).
Using a fork, mix until just combined. Taste and add salt, to taste.
Set two tostadas on a plate. Divide the tuna mixture evenly between the tostadas.
Add cubed avocado, a spoonful or two of chunky tomato salsa, and a drizzle of crema to each. Enjoy!
Notes
I purchased my tostadas, but you can certainly make your own tostadas.I used tuna packed in olive oil, but tuna packed in water works here too.