Blueberry Apricot Loaf Cake

STEP 1: COOK THE BLUEBERRY RIBBON

Finely zest the lemon and set the zest aside for the cake, then squeeze 2 teaspoons of juice. Combine the wild blueberries and sugar in a small heavy saucepan over medium heat. Cook, pressing the berries against the side of the pan, until they burst and release their juice, about 4 minutes. Mix the lemon juice with the cornstarch, stir it in, and simmer 2–3 minutes more, until thick enough that a spoon drawn through it leaves a clear trail. You should have about 1/2 cup. Cool, then chill until cold and thick, at least 30 minutes; a warm ribbon soaks into the crumb instead of sitting as a seam.

STEP 2: PREPARE THE PAN AND THE FRUIT

Heat the oven to 325°F (165°C) with a rack in the lower third. Grease the loaf pan and line it with a parchment sling over the long sides. Pat the diced apricots dry on paper towels. Toss the apricots and the frozen wild blueberries with the 1 tablespoon of flour, then return the bowl to the freezer until the fruit is folded in.

STEP 3: MAKE THE BATTER

Grind the freeze-dried blueberries to a fine powder and whisk them into the flour, baking powder and salt. Rub the reserved lemon zest into the sugar with your fingertips until fragrant. Beat the butter and lemon sugar on medium speed until very pale and fluffy, a full 5 minutes. Add the eggs one at a time, beating well after each and adding a spoonful of the flour mixture with the third and fourth eggs to stop the batter splitting. Beat in the vanilla extract. On low speed, add the remaining flour mixture in two additions, alternating with the milk, and stop as soon as no dry flour shows. The batter will be thick and faintly mauve.

STEP 4: FOLD IN THE FRUIT AND LAYER THE RIBBON

Fold the floured apricots and frozen blueberries through the batter with a rubber spatula, using as few strokes as possible. Spread just under half the batter in the pan. Spoon the cold blueberry ribbon in a strip down the middle, stopping 1/2 inch (1 cm) short of the sides and ends. Cover with the remaining batter and smooth the top. Run a lightly greased knife lengthwise down the center, about 1/2 inch (1 cm) deep, to give the loaf a clean central crack.

STEP 5: BAKE LOW AND SLOW

Bake for 70–80 minutes, until the loaf is deep golden, the crack looks dry, and a skewer pushed into the cake (away from the ribbon) comes out with no wet batter. The center should read 205–210°F (96–99°C) on an instant-read thermometer. If the top darkens too quickly, lay a sheet of foil loosely over it after 45 minutes. Expect a soft, moist crumb around the fruit.

STEP 6: COOL COMPLETELY

Cool in the pan on a wire rack for 20 minutes, then lift the loaf out by the parchment and let it cool completely, at least 2 hours. A fresh-fruit loaf cut warm will tear and look wet.

STEP 7: ICE AND DECORATE

Whisk the powdered sugar, vanilla and salt with 2 tablespoons of milk, then add more milk a few drops at a time until the icing is thick and flows slowly off the whisk. Spoon it along the top of the cold loaf and nudge it to the edges with a small offset spatula so it runs down the sides in a few places. Arrange the fresh blueberries and apricot wedges along the center while the icing is still wet. Let the icing set for 20 minutes before slicing with a serrated knife.