Mediterranean Lamb Burgers

Name: Mediterranean Lamb Burgers
Ingredients: 1 pound ground lamb; 0.5 pound ground beef; 3 tablespoons chopped fresh mint; 1 teaspoon minced fresh ginger root; 1 teaspoon minced garlic; 1 teaspoon salt; 0.5 teaspoon ground black pepper; 1 (16 ounce) container Greek yogurt; 0.5 lemon, zested; 1 clove garlic, minced; 0.5 teaspoon salt; 1 large sweet onion, cut into 1/2-inch slices; 4 slices green tomato; 4 ciabatta sandwich rolls, sliced horizontally; 1 (8 ounce) package feta cheese, sliced; 8 baby arugula leaves