Marinate the Steak
In a bowl, whisk together olive oil, red wine vinegar, Dijon mustard, honey, salt, Greek seasoning, and minced garlic. Coat the steak and let it marinate for at least 30 minutes (or up to 2 hours for deeper flavor).
Cook the Quinoa
In a saucepan, combine rinsed quinoa and water. Bring to a boil, reduce heat, cover, and simmer for 15 minutes, or until the liquid is absorbed. Fluff with a fork and set aside.
Grill or Sear the Steak
Heat a grill or stovetop skillet over medium-high heat. Cook the steak for 4-5 minutes per side, depending on thickness and desired doneness. Let the steak rest for 5-10 minutes, then slice thinly against the grain.
Assemble the Bowls
Divide cooked quinoa into serving bowls. Arrange baby spinach, cherry tomatoes, cucumber, red onion, Kalamata olives, and feta cheese on top. Add sliced steak and sprinkle with pistachios.
Garnish and Serve
Drizzle with tzatziki sauce and pomegranate molasses (if using) for an extra Mediterranean touch. Serve immediately and enjoy!