Grapefruit Olive Oil Cherry Swirl Loaf Cake:

• 3 tablespoons (10g) grapefruit zest, finely grated (from 1 grapefruit)
• 1 ⅓ cups (266g) white granulated sugar
• 6 ½ tablespoons (90g) olive oil (extra-virgin for pronounced flavor or regular for a muted flavor )
• 1 teaspoon (5g) kosher salt (I use Diamond Crystal, if using fine salt, add half the volume)
• 2 large (100g) eggs, room temperature
• 6 tablespoons (86g) full-fat sour cream, room temperature
• ½ cup (118g) water, room temperature
• 2 ¼ cups (270g) all-purpose flour, unbleached or bleached 
• 1 ½ teaspoons baking powder
• 6 tablespoons (180g) cherry jam (sour is best, but sweet will work too)

Grapefruit Soaking Syrup:

• about ½ cup (100g) of grapfruit juice (usually from half a large grapefruit, doesn’t have to be exact)
• ¼ cups (50g) white granulated sugar (plus more if needed)
• Zest of one extra grapefruit (optional, for candied zest garnish)

Buttery Grapefruit Glaze:

• 1 cup (113g) powdered sugar
• 2 tablespoons (28g) unsalted butter, softened
• 2 tablespoons (30g) of grapefruit soaking syrup, from above

1. Preheat oven: Place an oven rack in the middle of the oven and preheat the oven to 350°F/180°C.‍
2. Prepare pan: Prepare an 8-inch (also called a 1-lb) loaf pan by creating a parchment sling (see video) and apply a liberal coat of baking spray. ‍
3. Extract citrus oils: To a large mixing bowl, add the grapefruit zest and white granulated sugar. Massage with your fingers to release the fragrant citrus oils. Add the olive oil and salt. Mix on high speed for about two minutes.‍
4. Add liquids: Add the eggs and mix for a minute on high speed. Then add the sour cream and mix until completely incorporated. Add the water and mix on high speed for another minute. ‍
5. Add dry ingredients: Whisk together the flour and baking powder in a small bowl. Sift the flour mixture into the liquid batter in three additions, mixing after each addition until no visible flour remains.
   In a small bowl, add the cherry jam and about two spatula’s worth of batter. Stir until completely combined.‍
6. Bake loaf: Alternate pouring the grapefruit and cherry jam batter into the loaf pan. I like to pour the grapefruit batter in first to create consistent bottom layer, then dollop some cherry jam batter. Repeat a couple more times until all the batter is added, then take a skewer or butter knife to swirl the batter a little.
   Bake for about 1 hour and 20 minutes to 1 hour and 30 minutes. Start checking around an hour. The loaf is done when a skewer comes out with a few moist crumbs, or the internal temperature of the loaf is around 200°F/93°C. The final loaf will be domed in the center (with a possible split) and have a toasty brown crust on the sides and top.‍
7. Make Syrup: While baking your cake, make the syrup by adding grapefruit juice (from the one you zested earlier for the loaf) and sugar to a small saucepan.
   Optionally, you can remove the zest of an extra grapefruit for a candied zest topping to garnish the loaf. Add that to the syrup as well.
   Bring syrup to a boil and simmer for a few minutes. Let it sit until your loaf is done baking.
   Remove the candied zest to some parchment to dry and toss in sugar right before using.
   Set aside 2-3 tablespoons of this syrup in a small bowl for your frosting later.‍
8. Apply Syrup/Cool slightly: Once your loaf is done baking, remove it from the oven and carefully use the sling to remove it from the pan. Use a toothpick to poke some holes through the top. Brush some syrup atop the loaf.
   Flip the loaf onto one side using the sling, poke it with holes, and apply more syrup.
   Repeat for the remaining side.‍
9. Glaze loaf: Prepare the glaze by mixing the powdered sugar and butter until all the butter is incorporated. Add the reserved syrup and mix until all the sugar is mixed in. If you prefer a runnier glaze, add either more grapefruit juice, milk, or water until you like the consistency. I usually go for a pourable consistency that resembles a yogurt’s thickness.
   Pour the glaze atop the loaf, using a spatula to nudge the glaze for a drippy look. You can also decorate with candied orange zest if using. ‍
10. Storage: These citrus loaves taste amazing over the next few days. I’m comfortable leaving my loaf on my counter, wrapped tightly in plastic to keep the moisture in, but you can store your loaf in the fridge as well.