Season the steak

• Pat the steak dry and season generously with salt and pepper on both sides.

Sear the steak

• Heat the olive oil in a frying pan over high heat.
• Sear the steak until browned on both sides for the desired doneness.
• Add the butter and crushed garlic, spoon the foaming butter over the steak.

Rest the steak

• Transfer the steak to a board and let it rest before slicing.

Cook the onions

• In the same pan, soften the sliced onion until golden.

Toast the bread

• Toast the baguette halves cut side down in the pan until crisp.

Assemble the sandwich

• Spread mayonnaise on the toasted bread.
• Layer the lettuce, sliced steak, onions and cheddar cheese.
• Close the sandwich and serve.