1/2 cup plain yogurt
3 tablespoons vegetable oil
1 tablespoon lemon juice
2 egg whites
1/2 teaspoon lemon extract (optional)
1 1/2 cups all-purpose flour
3/4 cup white sugar
2 teaspoons baking powder
1/4 teaspoon salt
1 teaspoon grated lemon zest
1 cup frozen raspberries
2 tablespoons white sugar for decoration (optional)