1tablespoons2 sticks unsalted butter, softened but still cool
1 1/3cupssugar
3large eggs, at room temperature
3large egg yolk, at room temperature
1 1/2teaspoonsvanilla extract
1 1/2teaspoonswater
1/2teaspoonsalt
1 1/2cupsplain cake flour
Instructions
Adjust oven rack to center position and preheat oven to 325 degrees. Grease a 9 X 5 inch loaf pan and fit a piece of parchment paper lengthwise in the bottom of the pan, pushing it into the corners and up the sides.
In the bowl of a stand mixer fitted with the paddle attachment, beat butter at medium-high speed until smooth, about 15 seconds. With mixer still running, slowly sprinkle sugar into the bowl. Beat until light and fluffy about 4-5 minutes.
In a 2 cup measuring cup, combine eggs, egg yolks, vanilla, and water. With the mixer running, add egg mixture to the butter mixture in a slow and thin stream.
Sift 1/2 cup of cake flour into mixture and stir until just combined.Repeat twice more adding flour in 1/2 cup increments.
Place batter into prepared pan, smoothing the top with a spatula. Bake in preheated oven 70 to 80 minutes or until toothpick inserted into the middle of the crack comes out clean. Allow cake to rest in pan for 10 minutes before turning it out onto a wire rack to cool completely.