Season the tuna: Lightly coat both sides of the steak with Italian seasoning.
Sear: Heat a nonstick skillet over medium-high.
• Cook tuna 1½ minutes on the first side, then < 1 minute on the second (for a pink center).
• Transfer to a plate and let rest 2–3 minutes; then slice or flake into bite-sized pieces.
Mix the salad: In a bowl, combine tuna, celery, cherry tomatoes, jicama, and Napa cabbage.
• Sprinkle a bit more Italian seasoning.
• Stir in 2 Tbsp light mayo until evenly coated.
Build the wraps: Separate and rinse your romaine leaves; pat dry.
• Spoon a heaping 2–3 Tbsp of the tuna mixture onto each leaf.
• Fold or roll up like a burrito.