Preheat the Oven: Preheat your oven to 375°F (190°C). Line a baking sheet with parchment paper or lightly grease a loaf pan.
Sauté the Spinach: Heat 1 tablespoon of olive oil in a skillet over medium heat. Add the chopped spinach and cook for 1–2 minutes until wilted. Set aside to cool slightly.
Mix the Meatloaf: In a large bowl, combine the ground beef, sautéed spinach, feta cheese, onion, garlic, egg, breadcrumbs, parsley, oregano, cumin, salt, and pepper. If the mixture feels too dry, add milk or Greek yogurt. Mix until just combined; avoid overmixing.
Shape the Meatloaf: Transfer the meat mixture to the prepared baking sheet or loaf pan. Shape into a loaf or flatten slightly for even cooking.
Top and Bake: In a small bowl, mix the remaining olive oil and tomato paste. Spread this mixture over the top of the meatloaf for a flavorful glaze. Bake for 50–60 minutes, or until the internal temperature reaches 160°F (71°C).
Rest and Serve: Let the meatloaf rest for 10 minutes before slicing. Serve warm, garnished with additional parsley if desired.