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

In a bowl, whisk together sour cream or Greek yogurt, Dijon mustard, fresh herbs, garlic powder, salt, and pepper. Refrigerate for at least 10 minutes.

Slice zucchini into ¼-inch rounds, toss with olive oil, salt, and pepper. Grill for 2-3 minutes per side until tender.

Heat a grill pan, add olive oil, then cook the steak for about 3-4 minutes on each side for medium-rare. Let it rest for 5-10 minutes.

Assemble the bowl with cooked rice or mashed potatoes, layer grilled zucchini and sliced steak, and drizzle with herb sauce.