Caramelized Onion Steak Sandwich with Chives and Lemon Garlic Aioli

1. Start by generously rubbing salt on the steak, then place it in the fridge.
2. Thinly slice the onions. Melt 1 tbsp of butter with olive oil in a skillet over medium-low heat. Add the onions and stir occasionally until they are almost caramelized, about 20 minutes. Then, stir in the balsamic reduction and cook for another 5-10 minutes over low heat.
3. While the onions are cooking, whip up your aioli by simply combining mayonnaise, lemon juice, black pepper, and garlic. On the side, finely chop your chives so they’re ready.
4. Take the steak out of the fridge, pat it dry with a paper towel, season as you wish.
5. Heat 1 tbsp of neutral oil in a heavy-duty pan (cast iron or stainless steel) until it’s smoking hot. Sear your steak to a golden perfection. Flip the steak, then add 2 tbsp of butter, the rosemary sprig, and the garlic cloves. Baste continuously, cooking to your ideal doneness. Let the steak rest for at least 10 minutes before slicing.
6. Slice the ciabatta in half horizontally, then toast it in a pan with a little butter if desired.
7. Spread half the aioli on the bottom half of the loaf, then layer on the sliced steak, caramelized onions, and a sprinkle of chives. Spread the remaining aioli on the top half, then place it on top. Enjoy!