Greek Sandwich Wraps

Name: Greek Sandwich Wraps
Ingredients: 1 2 to 2 1/2-pound boneless lamb shoulder roast; 4 teaspoons Greek seasoning; ½ cup thinly sliced onion (1 medium); ¼ cup lemon juice; ½ cup light mayonnaise; 1 tablespoon Dijon mustard; 2 cloves garlic, minced; 8 (8 inch) flour tortillas (see Tip); ½ cup crumbled reduced-fat feta cheese; 2 cups shredded spinach; 1 ½ cups chopped cucumber (about 1 medium); ½ cup chopped tomato (1 medium)