In a medium bowl, whisk together olive oil, minced garlic, lemon juice, dried oregano, thyme, salt, and black pepper. Coat the sirloin steak and marinate at room temperature for 30 minutes or up to 4 hours in the fridge.

Rinse and grate cucumber for tzatziki, squeezing out moisture. Combine Greek yogurt, grated cucumber, lemon juice, and salt in a mixing bowl.

Heat a cast-iron skillet over medium-high heat. Sear the marinated steak for 4-5 minutes on each side for medium-rare. Let it rest for 5 minutes.

Slice the steak thinly against the grain.

Layer cooked grains in bowls, add sliced steak, cherry tomatoes, cucumber, red onion, and olives. Add feta, if desired.

Drizzle tzatziki and vinaigrette over the assembled bowls, garnishing with fresh herbs.