Marinate the Steak: In a mixing bowl, whisk together olive oil, minced garlic, lemon juice, oregano, thyme, salt, and pepper. Submerge the sirloin steak in this flavorful marinade, ensuring it's evenly coated. Cover and refrigerate for at least 30 minutes, or up to 4 hours, to allow the flavors to infuse and the steak to tenderize.

Prepare Tzatziki: Combine Greek yogurt, grated cucumber (squeezed dry), lemon juice, minced garlic, chopped dill, salt, and pepper in a separate bowl. Stir until well-blended, then cover and chill in the refrigerator.

Cook the Steak: Preheat a skillet over medium-high heat until hot. Sear the marinated steak in the skillet for about 4–5 minutes on each side until you achieve a nice brown crust and your desired doneness.

Assemble Bowls: Place cooked grains in each serving bowl, layer with sliced steak, add fresh vegetables like cherry tomatoes, cucumber, and red onion, and drizzle with tzatziki sauce.