Grapefruit Poppy Seed Cake

Preheat oven to 350°F (175°C). Grease and flour a 9×5-inch loaf pan or line with parchment paper.
In a medium bowl, whisk together flour, poppy seeds, baking powder, baking soda, and salt.
In a large mixing bowl, beat softened butter and granulated sugar until pale and fluffy, about 2–3 minutes.
Add eggs one at a time, beating well after each addition.
Mix in Greek yogurt or sour cream, grapefruit juice, grapefruit zest, and vanilla extract until smooth.
Gradually add the dry ingredients to the wet mixture, stirring until just combined. Do not overmix.
Pour batter into prepared loaf pan and smooth the top.
Bake for 45–50 minutes, or until a toothpick inserted in the center comes out clean or with a few moist crumbs.
Let the cake cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.
In a small bowl, whisk together powdered sugar and 2–3 tablespoons fresh grapefruit juice until smooth and pourable. Drizzle glaze over cooled cake and sprinkle with extra zest if desired.