Preheat and prep. Heat your oven to 375°F (190°C). Line a sheet pan with parchment or lightly oil a loaf pan. For best browning, shape the loaf free-form on a sheet pan rather than using a pan.

Wilt the spinach. Sauté chopped spinach in 1 teaspoon olive oil until just wilted, 1–2 minutes. Cool slightly and squeeze out any excess moisture. If using frozen spinach, thaw and squeeze dry in a clean towel.

Grate the onion. Use the large holes of a grater. The juices help keep the meat moist, so include them. Mince the garlic.

Mix the dry binders. In a large bowl, combine oats or breadcrumbs, oregano, cumin, dill, salt, and pepper. This spreads the seasoning evenly.

Add the wet ingredients. Stir in eggs, 1/2 cup Greek yogurt, grated onion (and juices), garlic, 1 tablespoon olive oil, lemon zest, and cooled spinach. Mix to form a thick, cohesive base.

Fold in the “Greek” bits. Gently mix in feta, olives, and sun-dried tomatoes if using. Don’t overmix or the loaf can get dense.

Add the turkey. Add ground turkey and mix with your hands just until combined. Stop as soon as it looks uniform.

Shape the loaf. Transfer to your prepared pan or sheet. Shape into a firm loaf about 9 x 5 inches. Smooth the top, then brush with the remaining 1 tablespoon olive oil for a golden finish.

Bake. Bake for 45–55 minutes, until an instant-read thermometer in the center reads 165°F (74°C). If the top browns too fast, tent loosely with foil.

Make the lemon-yogurt sauce. While it bakes, mix the remaining 1/2 cup Greek yogurt with 1–2 tablespoons lemon juice, a pinch of salt and pepper, and grated cucumber if using. Chill.

Rest and top. Let the meatloaf rest 10 minutes before slicing. Spoon some of the lemon-yogurt sauce over the top and serve the rest on the side.

Serve. Slice into 8–10 pieces. Great with roasted vegetables, a Greek salad, or warm pita and hummus.