1Heat oven to 350°F. Grease and flour 9-inch square pan. In medium bowl, mix 3/4 cup of the yogurt and the caramel topping; cover and refrigerate until serving time.
2In large bowl, beat remaining 1 1/4 cups yogurt and all remaining ingredients except apple and lemon juice with electric mixer on low speed 45 seconds, scraping bowl constantly. Beat on medium speed 1 minute, scraping bowl occasionally, until well blended. Stir in half of the chopped apple. Pour batter into pan. Sprinkle lemon juice over remaining apple; cover and refrigerate until serving time.
3Bake 38 to 43 minutes or until toothpick inserted in center comes out clean. Cool slightly. Serve with topping mixture and remaining chopped apple.