I thought this cake was fantastic. So so moist with the syrup made from the grapefruit (I may have indulged a bit in the syrup itself...or just used some in a glass of water to make grapefruitade of sorts). Be patient in letting the syrup soak into the cake...it takes time.
Ruby Red Grapefruit CakeSource: Ad Hoc at Home by Thomas Keller
Yield: One 9x4 loaf
2 cups all-purpose flour
1 3/4 teaspoons baking powder
1 teaspoon kosher salt
1 2/3 cups granulated sugar
2 large eggs
1 cup whole milk
3/4 cup canola oil
1 tablespoon grated ruby grapefruit zest
1 teaspoon vanilla paste or pure vanilla extract
1 cup strained fresh ruby grapefruit juice
2/3 cup granulated sugar
3/4 cup powdered sugar
1 tablespoon plus 1 teaspoon fresh ruby grapefruit juice
Preheat your oven to 350°F. Prep your pan by coating with a little non-stick spray or lightly oil.
Sift together the flour and baking soda and then whisk in the kosher salt. Set the mixture aside.
In the bowl of your stand mixer, using the whisk attachment, combine the eggs and sugar on medium speed for three minutes. The mixture should thicken, increase in volume and the whisk will leave a trail in the batter. Once everything looks right, beat in the milk, oil, then the zest and vanilla.
Reduce your mixer's speed to low and then beat in the flour, scraping the sides of the bowl as needed, until incorporated.
Pour the batter into your pan. Bake for an hour (rotating once).
While waiting for the cakes to bake, you can prep the grapefruit syrup.
Combine the grapefruit juice and sugar in a medium sauce pan over medium-high heat. Stir constantly until the sugar has dissolved. Bring to a boil, reduce heat to a simmer (it can boil over if left over high heat) and cook for 1 minute.
Once you pull your cake from the oven, poke holes into the cake with a wooden skewer. Brush your syrup over the cake, allowing it to absorb and then repeating until you've used up all the syrup. Allow the cake to cool in the pan completely before attempting to unmold.
To unmold, lightly coat a piece of waxed or parchment paper with a little oil or nonstick spray. Cover the cake with the paper and then invert. Turn the cake right-side-up onto a serving dish.
Whisk together the powdered sugar and grapefruit juice to make a glaze. Drizzle the glaze diagonally across the cake, allowing it to run down the sides. Slice and serve.
Keep the cake loosely covered at room temperature for up to two days.