Preheat the oven to 170 degrees Celsius. Prepare the baking pan by lining it with baking paper. Make sure to leave an overhand on the sides to make it easier to remove the cake from the pan after baking.
Combine the dry ingredients in a bowl using a hand whisk: flour, cornstarch, baking powder, and salt.
270 gs all-purpose flour, 30 gs cornstarch, 2.5 tsp baking powder, 3/4 tsp salt
In a bowl, add the softened butter and both the sugars, then whisk for 3-5 minutes on high speed using an electric or stand mixer until the mixture becomes pale and creamy.
170 gs unsalted butter softened, 150 gs packed brown sugar, 150 gs white sugar
Add the eggs into the batter, one at a time, and whisk on low speed for 30 seconds after every addition. Then, add the vanilla essence and whisk for another 30 seconds until well combined.
3 eggs, 2 tsp vanilla extract
Add the yogurt into the batter and whisk for 1-2 minutes on medium speed until it's fully combined. The batter may appear split at this point but it will come together once you add the dry ingredients.
240 gs full-fat yogurt, whisked
Add the dry ingredients and fold in the batter slowly using a silicone spatula and mix until just combined. Don't rush this process, you want the batter to retain as much air as possible.
In the prepared pan, pour half of the cake batter, then top it with the cinnamon filling. Pour the remaining batter on top of the filling, then top it with the cinnamon streusel crumb.
Bake the cake for 45-60 minutes*, until the top is golden brown, and a toothpick comes out clean from the center of the cake.
Let the cake cool, then top it with an an icing sugar and milk glaze and serve.