Here is one I've used and really enjoy--I'd make it more often, but real vanilla beans are expensive! It's a cupcake recipe, but I'm sure it would be fine for a cake.
Vanilla Bean Cupcakes
3 cups cake flour
1 tbsp. baking powder
½ tsp. salt
1 vanilla bean, split lengthwise
16 tbsp. unsalted butter, at room temperature
2 cups sugar
5 large eggs, at room temperature
1¼ cups buttermilk, at room temperature
1 tbsp. vanilla extract
Preheat the oven to 350° F. Line two cupcake pans with paper liners. Set aside.
In a medium mixing bowl, combine the cake flour, baking powder and salt. Whisk together and set aside. Add the butter to the bowl of an electric mixer fitted with the paddle attachment. Scrape the vanilla bean seeds into the bowl of the mixer with the butter and discard the pod (or reserve for another use.) Beat on medium-high speed for 3 minutes, until light and creamy in color. Scrape down the sides of the bowl and beat for one more minute.
Add the sugar to the butter mixture, ¼ cup at a time, beating 1 minute after each addition. Mix in the eggs one at a time until incorporated. Scrape down the sides of the bowl after each addition. Combine the buttermilk and the vanilla extract in a liquid measuring cup. With the mixer on low speed, add the dry ingredients alternately with the wet ingredients, beginning and ending with the dry ingredients and mixing just until incorporated. Scrape down the sides of the bowl and mix for 15 seconds longer.
Divide the batter between the prepared paper liners, filling each about 2/3 of the way full (you will likely have batter left over after filling 24 wells.) Bake 18-22 minutes, or until a toothpick inserted in the center comes out clean. Allow to cool in the pans 5-10 minutes, then transfer to a cooling rack to cool completely. Replace paper liners and bake remaining batter if desired. Frost cooled cupcakes as desired.
(I found the recipe online ages ago, but I don't know the original source)