Step 1

Heat the oven to 375°F with a rack in the middle position. Mist a 9-by-5-inch loaf pan with cooking spray, then line it with an 8-by-14-inch piece of kitchen parchment, allowing the excess to overhang the long sides of the pan. Mist the parchment with cooking spray.

Step 2

Place the clementines cut sides up in a medium microwave-safe bowl. Add 1 tablespoon water, cover and microwave on high until the fruits release some of their juice and their rinds soften, 6 to 8 minutes. Remove the bowl from the microwave (it will be very hot), and, using a slotted spoon, transfer the clementines to a blender jar. Cool for 15 to 20 minutes.

Step 3

Meanwhile, discard all but 2 tablespoons liquid in the bowl. Add the 2 tablespoons sugar to the liquid, then microwave uncovered on high for 30 seconds. Remove from the microwave and whisk until the sugar dissolves; set the syrup aside for brushing the baked cake. In a large bowl, whisk together the flour, baking powder and salt.

Step 4

To the partially cooled clementines in the blender, add the remaining 268 grams (1 ¼ cups) sugar, the eggs, butter and vanilla. Blend until smooth, 1 to 2 minutes, scraping the jar as needed. Pour the puree into the flour mixture, then whisk just until smooth and well combined; the mixture will resemble pancake batter. Transfer to the prepared pan and rap the pan against the counter to remove any air bubbles.

Step 5

Bake until deep golden brown and a skewer inserted at the center comes out with just a few crumbs attached, 45 to 55 minutes. Cool in the pan on a wire rack for 10 minutes, then lift the loaf out of the pan using the parchment and set it directly on the rack. Carefully slide the cake off of the parchment and brush all over with the reserved syrup. Cool completely before serving.