Melt butter in a sauté pan on medium heat. Once the butter is melted, add sliced onions, cook, stirring often, until caramelized (soft + brown). This will take approximately 10-15 minutes. In a larger pan, heat avocado oil on medium. Place lettuce on desired serving platter and top with onions, steak, cherry tomatoes, cranberries and feta cheese. Serve as is or toss with one of recommended salad dressings.