Preheat the oven to 350°F. Line cupcake pans with paper cases and set aside.

Sift the flours, dried buttermilk, baking powder, and salt into a bowl. Whisk to combine, then set aside.

Add the butter, sugars, and cake enhancer (if using) to the bowl of a stand mixer fitted with a paddle attachment. Cream on a medium speed until light and fluffy, about 5 minutes. Make sure to scrape the bowl down once or twice during the process.

Add the vanilla to the bowl and beat on medium until well combined, about 1 minute. Scrape the bowl down.

With the mixer on the lowest speed, add an egg and mix for about 15 seconds before bumping the speed up to the next lowest setting. Mix until combined, about 15 seconds more. Repeat the process with the remaining eggs, scraping the bowl down occasionally.

As the eggs finish incorporating, combine the water and oil, then set aside.

Alternate adding dry and wet ingredients. Begin with a third of the dry and mix on the lowest speed until just combined. Drizzle in half of the liquids and beat on low until nearly combined. Scrape the bowl down and repeat this process with another addition of dry, then wet ingredients. Scrape the bowl down and finish with the final bit of dry ingredients. Mix until just combined.

Use a cupcake scoop to divide the batter among the cupcake pans. Bake for 20- 22 minutes, or until the cupcakes spring back when tapped on top and a skewer comes out clean.

Cool in the pans for about 5 minutes before transferring the cupcakes to a cooling rack.

In a stand mixer fitted with a paddle attachment, beat the butter until smooth and light, about 4 minutes. Scrape the bowl down and add the cream cheese. Beat until combined and light, another 4 minutes.

Add about one third of the powdered sugar. Beat for 1- 2 minutes, starting on low and bumping up to medium. Add another third of the sugar. Beat for another minute. Add the remaining powdered sugar, lemon juice (if using), and vanilla. Beat for a minute or two until combined and smooth.