Pat the steak dry and season both sides with garlic powder, onion powder, salt, and pepper. Let it rest for 15–20 minutes.
Combine sour cream or Greek yogurt, Dijon mustard, chopped fresh herbs, garlic powder, salt, and pepper in a bowl. Whisk until smooth and refrigerate.
Toss zucchini slices in olive oil along with salt and pepper. Grill on medium-high heat for 2–3 minutes per side until tender and charred.
Heat a grill pan or skillet over medium-high heat. Cook each side of the steak for 3–4 minutes until medium-rare. Let it rest for 5–10 minutes before slicing.
Assemble the bowl by layering cooked rice or mashed potatoes, grilled zucchini, sliced steak, and drizzle with creamy herb sauce.