Step 1

Preheat the oven to 325 degrees. Spray two 8 1/2 x 4 1/2 x 2 1/2-inch metal loaf pans with the baking spray and sprinkle the insides of the pans with the demerara sugar, tilting the pans to cover evenly.

Step 2

Place the butter, cream cheese, and granulated sugar in the bowl of an electric mixer fitted with the paddle attachment and beat on medium speed for 2 1/2 to 3 minutes, until light and creamy. Scrape down the bowl with a rubber spatula to be sure it's well mixed. With the mixer on low, add the eggs, one at a time, mixing well and scraping down the bowl before adding the next egg. Mix in the vanilla extract and vanilla seeds.

Step 3

Combine the cake flour and salt in a medium bowl. With the mixer on low, slowly add the flour mixture to the butter mixture, scraping down the bowl and beater with a rubber spatula. Mix the batter with the spatula to be sure it's well mixed. Divide the batter evenly between the two loaf pans, smooth the tops, and bake in the center of the oven for 60 to 70 minutes, until a toothpick inserted into the center of each cake comes out clean.

Step 4

Allow the cakes to cool in the pans for 30 minutes, then carefully turn them out and cool completely on a baking rack.