Feta-Stuffed Lamb Burgers with Tzatziki

I wanted to make a lighter dinner, so I found this recipe in a Weight Watchers cookbook.    Instead of making larger burgers, I made smaller meatballs and put two meatballs in a pita pocket.  The meatballs were good, but the tzatziki sauce wasn't as successful.  

Feta-Stuffed Lamb Burgers  (2013 Cookbook Challenge)
(Recipe adapted from Weight Watchers Cook It Quick Cookbook
Makes 4 servings; 350 calories/serving

Ingredients:
1 pound lean ground lamb
1 teaspoon salt
1/2 teaspoon freshly ground black pepper
1/2 teaspoon garlic powder
2 teaspoons minced rosemary leaves
6 tablespoons crumbled feta cheese, reduced-fat
4 large romaine lettuce leaves
4 pita pockets (I used Brownberry Italian Herb Flatbread Pocket Thins) 
1/2 cup tzatziki (see recipe below)

Directions:
Combine the lamb, seasonings, and feta cheese and form into 4 burgers or 8 meatballs.  Cook the burgers in a nonstick skillet until browned, turning to brown each side, about 7-10 minutes total.

Place a lettuce leaf in each pita pocket, followed by the burger, and top with 2 tablespoons tzatziki.

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Tzatziki Recipe

1 cup grated seeded peeled cucumber
1 cup plain fat-free Greek yogurt
1 tablespoon chopped fresh mint
2 teaspoons chopped fresh dill
2 teaspoons fresh lemon juice
1/4 teaspoon salt
2 garlic cloves, minced

Combine all ingredients until well blended.  Refrigerate at least an hour before serving.