Beef tenderloin steaks with Balsamic green beans

2 tsp butter, divided
1 c vertically sliced yellow onion
1 c vertically sliced red onion
1/4 c sliced shallots
3 garlic cloves, minced
1/2 c beef broth
2 c green beans trimmed
1/4 tsp salt divided
4 (4 oz) beef tenderloin steaks
1/3 tsp black pepper

Melt 1 tsp butter in a medium saucepan over medium high heat. Add onions and shallots, saute 6 minutes. Add garlic; saute 1 minute. Add broth; cook 4 minutes or until onions are tender and liquid is almost evaporated. Add beans and vinegar, cover and cook 4 minutes. Remove from heat. Stir in remain 1 tsp of butter and 1/8 salt; keep warm.
Sprinkle steaks with salt and pepper. heat a cast-iron skillet over medium high heat. Add steaks and cook 3 minutes per side or until desired doneness. Let rest 5 minutes

Serving Size: 4 servings 1 steak and 1/2 c bean mix