"This is a savory steak with the slight sweetness of caramelized onions and the earthiness of truffle oil. I would serve this with some mashed goat cheese and a nice green veggie. This recipe could be for 2, you and your honey! A nice Cabernet would pair well, but I like so many that it's hard to choose. Cheers."
Heat 2 tablespoons oil in a saucepan over medium-high heat. Add onions; cook, stirring occasionally, until onions are dark and soft, about 25 minutes.
Mix butter, shallot, and truffle oil in a bowl until blended. Refrigerate until set, about 10 minutes.
Preheat an oven-safe skillet over medium-high heat. Pour in remaining 2 tablespoons oil. Season steaks with salt and pepper on both sides. Cook steaks until browned, about 2 minutes per side. Cover with aluminum foil.
Transfer skillet to the preheated oven and bake until steaks are reddish-pink and juicy in the center, 4 to 6 minutes. An instant-read thermometer inserted into the center should read 130 degrees F (54 degrees C). Let rest in the skillet, covered, about 5 minutes.
Slice steaks and transfer to serving plates. Cover with onions; top with a slice of truffle butter.