Finely chop the tuna and onion.
Beat the eggs and mix with tuna, onion, mayonnaise, salt, and pepper.
Heat oil in a pan over medium-low heat.
Pour a thin layer of the egg mixture into the pan; when it sets slightly, roll it up.
Repeat pouring and rolling with the remaining mixture until used up.
Cook until golden, then slice the finished egg roll into bite-size pieces.