Prep the lettuce: Chop romaine into bite-size pieces.
Rinse and spin dry very well. Wet leaves dilute the dressing, so get them as dry as you can.
Make the dressing base: In a bowl, whisk Greek yogurt, mayonnaise, lemon juice, Dijon, Worcestershire, garlic, and anchovy. It should be smooth and creamy.
Add cheese and oil: Whisk in Parmesan, then slowly stream in the olive oil until it’s glossy.
Season with salt and plenty of black pepper. Taste and adjust lemon or salt as needed.
Prep the tuna: Drain tuna thoroughly. Flake gently with a fork.
If using oil-packed tuna, drain lightly but keep a little oil for flavor.
Toss the greens: In a large bowl, add romaine and a generous amount of dressing. Toss with tongs until every leaf is lightly coated.
Assemble: Gently fold in the tuna so it stays in chunky pieces. Add croutons and a handful of extra Parmesan.
If using add-ins like tomatoes or chickpeas, fold them in now.
Finish and serve: Top with cracked black pepper and a squeeze of lemon. Serve immediately so the lettuce stays crisp and the croutons crunchy.