Preheat an oven to 180c (350f) and prepare a 9x9 inch cake pan with parchment paper.
In a large mixing bowl add the room-temperature butter, granulated sugar, vanilla extract, and salt, and mix with an electric hand mixer until smooth and creamy for about 3 minutes.
Add the eggs and mix until smooth and well combined.
Add the sour cream and mix until well combined.
Add ½ of the buttermilk, ½ of the flour, and baking powder, and baking soda, and mix it until almost combined.
Add the other half of the flour and buttermilk and mix until just combined. Do not overmix to keep the cake moist.
Pour the cake batter into the prepared pan and spread it with an offset spatula.
Bake in a 180c (350f) oven for about 45-50 minutes (depending on the oven) or until a toothpick inserted into the cake comes out clean with a few moist crumbs.
Allow the cake to cool to room temperature for at least 1 hour.
Notes
Use room temperature ingredients. Ensure your butter, eggs, and milk are at room temperature for better incorporation and a smoother batter.
Sift the flour, baking powder, baking soda and salt together to remove lumps and ensure even distribution.
Alternate wet and dry ingredients. Add dry ingredients and milk alternately to the creamed mixture, beginning and ending with dry ingredients. This prevents overmixing.
Creaming the butter and sugar together until light and fluffy is essential for a tender crumb in your cake. Take your time with this step for the best results.
Measure your flour correctly! When measuring your flour, avoid scooping it with a measuring cup. Instead, stir the flour with a spoon to create as many air pockets as possible, and spoon it into your measuring cup. Finally, level it with a back of a knife.
Test for doneness: Use a toothpick or cake tester inserted into the center. It should come out clean or with a few moist crumbs.
Don’t overmix the batter, you don’t want to develop the gluten in the flour. This step ensures you have a moist cake and not a dense and dry cake.
Line your baking pan with parchment paper! This step helps the cake to bake evenly, and it makes sure that your cake will release easily from the pan.
Allow the cake to cool in the pan for 10-15 minutes before transferring to a wire rack. This prevents it from breaking or sticking.