Wonderful Avocado Butter over Grilled Flank Steak

WONDERFUL AVOCADO BUTTER OVER GRILLED FLANK STEAK
8 T. butter, room temp
½ large ripe avocado, small dice
1 (6 oz.) fresh pico de gallo
2 T. finely chopped fresh cilantro
1 T. fresh lime juice
1 t. finely chopped serrano
1 t. toasted ground coriander
Kosher salt/black pepper
2 T. olive oil
1 T. garlic powder
1 T. dark brown sugar
1 t. chili powder
2 lb. flank steak

1. In bowl, combine butter, avocado, pico, cilantro, lime juice, serrano, coriander, salt and black pepper. Mix well. Cover and refrigerate until needed. Can be made a day or two ahead.
2. In saucepan over medium heat, combine oil, garlic, brown sugar, chili powder, salt and pepper.
3. Cook, stir occasionally, until sugar dissolves.
4. Allow mixture to cool. Rub all over flank steak. Let sit for 30 minutes or overnight.
5. Heat grill to 400-475.
6. Let steak sit at room temp for 1 hour. Grill steak, flip once, until medium rare (125 degrees), about 8 minutes.
7. Transfer to cutting board, smear with a good amount of the butter mixture, tent with foil and let rest 8-10 minutes.
8. Slice against grain and serve with remaining butter.