Add to a large bowl your melted butter, brown sugar, white sugar, vanilla extract and condensed milk. Using a whisk, of a hand mixer, mix until fully combined. Your mixture should be very light.
Add one egg at a time and mix until fully incorporated
Add in your pumpkin puree, whole milk and vinegar. Mix again.
Mix your dry ingredients together and add to your wet ingredient bowl. Using a spatula, carefully fold in your cake batter. Make sure that you continue mixing it in by hand until all dry and wet are perfectly combined.
Line a 12x4.5 loaf tin (see notes) with parchment paper or brush with oil and dust with flour. Pour your batter into the tin an carefully spread it. OPTIONAL : drizzle 2 tbsp of white sugar on top of your cake batter to get a crispy sugary crust.
Bake for 60-75 minutes. To make sure that your cake is done, poke it with a toothpick in the middle, if it comes out clean, then you're good to go. Serve & Enjoy.