Preheat oven to 350 F.
Grease a 9x5x3-inch loaf pan. In a large mixing bowl beat together granulated sugar, Greek yogurt, eggs, and vanilla on low speed using an electric mixer. Mix until combined turn up to medium speed for 2 minutes.
In a medium bowl stir together flour, baking powder, soda, and salt; add to yogurt mixture. Beat on low speed until combined. Stir in apples. Turn into prepared loaf pan.
For topping; mix together butter, sugar and cinnamon. Spoon over batter.
Bake for 55 to 60 minutes or until a wooden toothpick inserted in center comes out clean. (If necessary, cover loosely with foil the last 10 minutes of baking to prevent overbrowning.) Cool in pan on a wire rack for 10 minutes.