Preheat the oven to 350F (180C).
In a large bowl, whisk yogurt and eggs.
200 grams thick plane yogurt, room temperature, or sour cream, 2 eggs, room temperature
Mix in the sugar and vanilla extract until smooth.
200 grams granulated brown sugar, 2 teaspoons vanilla extract
Pour in the melted butter and mix it in.
56 grams melted butter
In another bowl, whisk the flour, cinnamon, baking powder, baking soda, and salt. Add the flour mixture to the wet ingredients. Whisk just until no dry pockets remain. Don’t overmix. Set aside.
260 grams all-purpose flour, 1 teaspoon cinnamon, 1 teaspoon baking powder, ½ teaspoon baking soda, ¼ teaspoon salt
Peel, core, and grate the apple. Add the grated apple to the batter and mix it gently.
160 grams apple (1 medium apple)
Place a parchment paper in a 9x4.5 inch (23x11 cm) loaf tin. Transfer the batter to the baking dish.
Chop the walnuts and add them evenly on top of the batter. Sprinkle on top one tablespoon of granulated brown sugar, such as demerara or turbinado.
50 grams raw walnuts, 1 tablespoon granulated brown sugar
Bake on the middle rack for 55 minutes or until a toothpick (skewer) comes out clean when inserted into the center of the loaf.