Step 1
Preheat grill to medium high heat.Season red onion rings and mushrooms with 1 tablespoon olive oil, salt and pepper to taste.
Step 2
Place onion rings and mushrooms on grill. Grill for 4-5 minutes per side until char marks appear.
Step 3
Remove and set aside.Take steak out of your fridge and let it sit in the room temperature for 5 minutes. Use a paper towel to gently pat the surface of both sides of the steak dry.
Step 4
Brush olive oil on both sides of the steak or use olive oil cooking spray. Generously season the steak with salt and freshly ground pepper.
Step 5
Place the steak on the grill. Grill each side for 3-5 minutes until the internal temperature of the steak reaches 145°F for medium doneness; 135°F for medium rare and 155°F for medium well.
Step 6
Let rest for 5 minutes before slicing.To make the Chimichurri sauce, place all ingredients in a food processor, blend for about 30 seconds or until all ingredients are combined well (any remaining sauce can be stored in the refrigerator for up to 2 weeks).To assemble, arrange baby spinach spring mix on the bottom of a large serving plate, followed by the onion rings and mushrooms. Slice the steak and place on top of the vegetables. Top with cherry tomatoes and sliced avocado.
Step 7
Drizzle the Chimichurri sauce over the steak salad and serve!