Pat the steak dry with paper towels and season both sides with garlic powder, onion powder, salt, and pepper. Let rest for 15-20 minutes.

In a bowl, whisk together sour cream or Greek yogurt, Dijon mustard, chopped fresh herbs, garlic powder, salt, and pepper until smooth. Refrigerate for at least 15 minutes.

Slice zucchini into rounds, toss with olive oil, salt, and pepper. Grill over medium-high heat for 2-3 minutes per side until tender.

Heat grill pan over medium-high heat. Cook steak for 3-4 minutes on each side for medium-rare, checking for 130°F internal temperature. Let rest for 5-10 minutes.

Layer rice or mashed potatoes in a bowl, top with grilled zucchini and sliced steak, and drizzle the creamy herb sauce over. Garnish with additional herbs if desired.