Grilled Steak Salad with Dijon Vinaigrette Recipe

INGREDIENTS

3/4 lb

flat iron steak

medium onion, sliced

2 tsp

butter

1/3 cup

plus two teaspoons olive oil

2 tbsp

red wine vinegar

1 tbsp

Dijon mustard

1/2 tsp

garlic powder

2 tsp

Worcestershire sauce

1/4 tsp

kosher salt (plus more for seasoning steak)

1/4 tsp

pepper (plus more for seasoning steak)

2 1/2 oz

baby romaine leaves

2 1/2 oz

baby spinach leaves

1 cup

thinly sliced crimini mushrooms