DO-AHEAD TIP: Cook ground beef.
In a small bowl, combine yogurt, cucumber and dill. Cover and refrigerate. Heat the olive oil in a large skillet over medium-high heat.
Add onion rings and cook for 2 minutes, stirring occasionally. Add cooked ground beef, garlic powder and oregano.
Cook for 4 minutes or until heated through, stirring occasionally.
Stuff beef mixture in warmed pita breads. Serve with yogurt sauce and garnish with chopped tomato. Enjoy!!!