Preheat the oven to 350°F.
Line an 8” or 9” springform pan with parchment paper and spray it with oil. If using an 8″ pan, make sure it’s deep. You can also use a regular 9″ cake pan.
In a medium bowl, whisk together flour, baking powder, baking soda, and salt. Set aside.
In a large mixing bowl or stand mixer, beat the butter at medium speed for 30 seconds.
Add granulated and brown sugar, and beat for 2 more minutes until light and fluffy. Scrape the bowl occasionally.
Add eggs, one at a time, mixing until each is incorporated. Add vanilla and mix.
Add sour cream and mix.
Add half the dry ingredients and mix on low.
Pour in the buttermilk and mix.
Add the remaining dry ingredients and mix on low. Avoid over-mixing to prevent dryness.
Spread the batter in the prepared pan.