Preheat your oven to 400°F. Slice off the top of a head of garlic to expose the cloves. Drizzle with olive oil and sprinkle with salt. Wrap in foil and roast for about 40 minutes, or until the cloves are golden and buttery-soft.
For the Fried Onions
Thinly slice one onion and soak the slices in a bowl with buttermilk and a few dashes of hot sauce for 10–15 minutes.In a separate bowl, combine your seasoned flour mixture. Working in batches, remove onions from the buttermilk, coat in the flour mix, and fry in oil over medium heat until golden and crispy. Transfer to a paper towel–lined plate and sprinkle with salt while hot, if desired.
For the steak
Bring the steak to room temperature and pat dry to remove moisture—this helps with searing. Generously season all sides with kosher salt and freshly cracked black pepper, pressing the seasoning into the meat.
Heat a cast iron skillet over medium-high heat with a drizzle of neutral oil.Start by searing the fat cap, then sear both sides—about 3 minutes on the first side, 1 minute on the second.
Reduce heat to medium and add unsalted butter, smashed garlic cloves, and thyme or rosemary. Tilt the pan and baste the steak continuously with the melted butter and aromatics until it reaches your desired doneness.Let rest before slicing.
For the garlic aioli
In a small bowl, combine roasted garlic, Kewpie mayo, a few drops of white truffle oil, a squeeze of fresh lemon juice, salt, and pepper to taste.
To Assemble
Drizzle the inside of ciabatta bread with olive oil and toast until golden. Spread garlic aioli on both slices. Layer on the sliced steak, Caesar salad, and crispy fried onions. Top with the second slice of bread, slice in half, and enjoy!