> 2 tbsp olive oil, divided
> 2 tbsp butter
> 2 onions, thinly sliced
> 1 lb 90% lean ground beef
> 1 (1 oz) pkg onion soup & dip mix
> 4 hamburger buns or split ciabatta rolls
> 4 slices Swiss cheese
In a large skillet over medium-high, heat 1 tbsp oil and butter. Add the onions and season with salt. Sauté 5 min., until beginning to brown. Add 2 tbsp water and scrape up any brown bits on bottom of skillet with a wooden spoon. Reduce heat to low and cook 20 min., until onions are caramelized, stirring occasionally.
Meanwhile, in a medium bowl, combine the beef and onion soup mix. Season with salt and pepper. Shape into 4 equal-size patties. Grease grill or grill pan and set to medium. Brush cut sides of the buns or rolls with remaining 1 tbsp oil. Place bread on grill and heat until toasted, 1–2 min. per side.
Place patties on grill or grill pan and cook 3–4 min. per side, until desired doneness. During last minute of cooking, place 1 slice cheese on each burger and cover to melt. Serve on grilled rolls and top with caramelized onions.