Chocolate Loaf Cake with Raspberry Filling

Steps

1. Make the filling first: in a small saucepan, combine the raspberries, the 30 g portion of the sugar and the lemon juice. Cook over medium heat, mashing lightly, until the berries break down and bubble, about 5 minutes.
2. Stir the cornstarch into the cold water until smooth, then stir this slurry into the raspberries. Simmer 1 to 2 minutes, stirring, until thick and glossy. Spread the filling on a plate and refrigerate about 20 minutes until cool and spreadable.
3. While the filling cools, preheat the oven to 350°F (175°C). Brush a 9x5-inch loaf pan with about 1 teaspoon of the canola oil and line it with a parchment sling.
4. In a large bowl, whisk the flour, the sifted unsweetened cocoa powder, the baking soda, the baking powder and the salt until evenly combined.
5. In a second bowl, whisk the eggs with the remaining 180 g of sugar until slightly pale, about 1 minute. Whisk in the buttermilk, the rest of the canola oil and the vanilla.
6. Pour the egg mixture into the cocoa-flour mixture and fold with a spatula just until no dry streaks remain.
7. Spread half of the batter in the pan. Spoon the cooled raspberry filling over it in an even layer, leaving a 1/2-inch border at the edges. Cover with the remaining half of the batter and smooth the top.
8. Bake 60 to 65 minutes, until the top springs back and a toothpick inserted into the cake (not the filling) comes out clean. Tent loosely with foil after 40 minutes if the top darkens.
9. Cool in the pan on a rack for 15 minutes, lift out with the parchment, and cool completely on the rack, about 1 1/2 hours, so the filling sets.
10. Slice into 12 pieces with a serrated knife, wiping the blade between cuts.