Preheat oven to 350 degrees F. Line bottom of a 9x9x2-inch baking pan with parchment paper or foil; set aside.
In large bowl combine egg, yogurt, onion, bread crumbs, oregano, mint, lemon peel, garlic, and 1/2 tsp. salt. Add beef and 1/3 cup feta cheese. Mix lightly to combine. Evenly spread meat mixture into prepared baking pan, pressing into the corners and shaping a flat top. Unlike most meat loaves, the Weeknight Meat Loaf lets the pan do the work. Evenly press meat mixture into a 9-inch square baking pan, making sure to push mixture into the corners. Pat the surface flat and top with tomato and lemon slices.
Bake 45 to 50 minutes or until an instant-read thermometer inserted in center of loaf reads 160 degrees F. Spoon or pour off fat. Let loaf stand 10 minutes. To serve, cut in squares; top with lemon, chopped cucumber, and mint. Serve with feta cheese and Herbed Potatoes. Makes 9 servings.
In large bowl, combine potatoes and olive oil. Place sliced potatoes on shallow parchment-lined baking pan. Bake in oven with meat loaf at 350 degrees F for 45 minutes, stirring occasionally. Remove from oven. Sprinkle with rosemary, salt and pepper. Makes 9 servings.