Instructions

• Preheat the oven to 350°F (180°C). Grease an 8- or 9-inch cake pan and line the bottom with parchment paper (if available).
• In a medium bowl, whisk together 1½ cups all-purpose flour, 1 teaspoon baking powder, 1 teaspoon baking soda, 1 teaspoon ground cinnamon, and ½ teaspoon salt. Set aside.
• In a separate large bowl, beat ¾ cup melted butter with 1 cup granulated sugar until smooth and creamy. Add the 2 large eggs (at room temperature) and beat until combined.
• Stir in 1 cup plain yogurt and the splash of vinegar from the ingredient list; mix until smooth.
• Add the dry ingredients to the wet ingredients and mix gently until just combined. Do not overmix.
• Fold in the 2 cups chopped and peeled apples until evenly distributed.
• Pour the batter into the prepared pan and smooth the top.
• To make the streusel, combine ¾ cup granulated sugar, 1 teaspoon ground cinnamon, and ½ cup chopped walnuts in a small bowl. Sprinkle the streusel evenly over the batter.
• Bake in the preheated oven for about 50 minutes, or until a toothpick inserted into the center comes out clean.
• Remove the cake from the oven and let it cool in the pan for 10 minutes. Then remove the cake from the pan and transfer it to a wire rack to cool completely.
• When cooled, slice and serve.