1 1/2 cups all-purpose flour
2 teaspoons baking powder
1/2 teaspoon kosher salt
1 cup plain whole-milk yogurt
1 cup sugar
zest from 1 large grapefruit
1/2 teaspoon pure vanilla extract
1/4 cup vegetable oil
Preheat the oven to 350°F. Grease an 8 1/2 by 4 1/4 by 2 1/2-inch loaf pan. Line the bottom with parchment paper. Grease and flour the pan.Sift together the flour, baking powder, and salt into 1 bowl.
In another bowl, whisk together the yogurt, 1 cup sugar, the eggs, grapefruit zest, and vanilla. Slowly whisk the dry ingredients into the wet ingredients. With a rubber spatula, fold the vegetable oil into the batter, making sure it’s all incorporated. Pour the batter into the prepared pan and bake for about 50 minutes, or until a cake tester placed in the center of the loaf comes out clean.
For the glaze - mix powdered sugar and grapefruit juice until desired consistency is reached. Pour over the cake while it is still warm.