Preheat the oven to 350F. Grease and line a 9-inch loaf pan with parchment paper.

Add the sugar and grapefruit zest to a large bowl. Use your hands to rub the zest into the sugar, releasing the oils.

Add the milk, olive oil, eggs, and vanilla extract. Whisk until combined.

Add the flour, baking powder, baking soda, and salt. Use a rubber spatula to gently mix until just combined, a few lumps may remain.

Pour the batter into the prepared loaf pan. Transfer to the oven and bake for 40-55 minutes, until an inserted toothpick comes out clean. Let the loaf cool in the pan for 15 minutes, then transfer to a cooling rack to cool completely.

While the loaf cools, make the topping. Add the heavy cream and sugar to a medium bowl. Use a stand or hand mixer to mix until soft peaks form, about 3 to 5 minutes.

Add the yogurt and vanilla extract. Mix until stiff peaks form, 1 to 2 minutes.

When the loaf is completely cooled, slice the loaf and top each slice with a dollop of the whipped cream yogurt. Drizzle with olive oil and enjoy!