Prep the steak: Pat the steak dry with paper towels.
Season both sides with salt and pepper. Let it sit at room temperature for 20–30 minutes while you prep the salad components.
Make the croutons (if using): Heat the oven to 375°F (190°C). Toss bread cubes with olive oil, garlic powder, salt, and pepper.
Spread on a sheet pan and bake 8–12 minutes, stirring once, until golden and crisp. Cool slightly.
Whisk the dressing: In a bowl, mash anchovies with the grated garlic to form a paste. Whisk in egg yolk (or mayo), Dijon, and lemon juice.
Slowly stream in olive oil while whisking until thick and glossy. Stir in Parmesan. Season with salt and pepper.
Thin with a teaspoon of water if needed.
Prep the salad base: Add romaine to a large bowl. Keep Parmesan and croutons nearby. You’ll dress it just before serving to keep everything crisp.
Sear the steak: Heat a heavy skillet (cast iron is ideal) over medium-high until very hot.
Add olive oil. Lay in the steak and sear 3–4 minutes without moving it. Flip and cook another 2–4 minutes until it’s near your desired doneness.
Add the garlic butter: Reduce heat to medium-low.
Add butter, smashed garlic, and herbs to the pan. Tilt the pan and spoon the foaming butter over the steak for 1–2 minutes. Aim for an internal temperature of 125–130°F for medium-rare, 135°F for medium.
Rest and slice: Transfer steak to a cutting board and rest 5–10 minutes.
Slice thinly against the grain. Spoon any garlicky pan butter over the slices.
Dress the salad: Toss romaine with enough Caesar dressing to lightly coat. Add croutons and shaved Parmesan.
Toss again gently. Taste and adjust with extra lemon, salt, or pepper.
Assemble and serve: Pile the dressed salad onto plates. Top with warm steak slices.
Finish with a drizzle of remaining garlic butter and a squeeze of lemon. Serve right away.