Grease a 6 by 2 inch pan and line with a parchment paper. Preheat the oven at 170 C for at least 15 mins.
Bring all ingredients to room temperature. Wash and peel the apples. Chop and puree them in a mixer. For this apple cake we need only ½ cup puree.
Mix together milk, vinegar, melted butter, sugar and ½ cup apple puree in a large mixing bowl. Rest for 5 mins and whisk well until it turns uniform. It's just fine if the sugar does not dissolve completely.
Place a sieve over the mixing bowl and add flour, baking soda, baking powder, & cinnamon. Gently mix them with a fork and sieve to the bowl.
Mix the wet & dry ingredients using a spatula just until combined. Do not over mix.
Pour the batter to the cake pan. Tap it on the counter a few times.
Bake it for 25 to 30 mins. Mine takes about 26 to 29 mins. This may vary depending on the oven.
A tester inserted comes out clean it with slight crumbs. Cool the pan on a wire rack for 5 mins.
Gently invert it on a wire rack. The cake is delicate so handle with care.
Allow apple cake to cool completely and slice. You can dust some powdered sugar or drizzle some melted chocolate.