Cut the avocados in half lengthwise and carefully remove the pits. Scoop out some flesh to create room for stuffing.

In a bowl, combine canned tuna, chopped red onion, mayonnaise, lemon juice, salt, and pepper. Mix until well blended.

Generously spoon the tuna mixture into each avocado half.

Garnish with additional salt and pepper if desired, and add fresh herbs like parsley or cilantro.

Serve immediately for the best flavor and freshness.