- Preheat the oven to 325°F (160°C). Grease a 9 × 5-inch (2 L) loaf pan and line the bottom and sides with parchment paper.
- For the crumble, stir the flour, sugar, lemon zest, baking powder and salt together. Add the melted butter and stir with a fork until the mixture is rough and crumbly (it will be soft). Set aside.
- For the cake, sift the flour, sugar, baking powder and salt into a large mixing bowl if using electric beaters, or into the bowl of a stand mixer fitted with the paddle attachment. Add the butter and lemon zest and beat on low speed until large pieces of butter are no longer visible.
- In a bowl, whisk the sour cream, eggs, egg yolk and vanilla together. Add all at once to the flour mixture and beat on low speed until the batter is moistened. Increase the speed to medium, mixing until the batter is smooth, about 30 seconds (the batter will be thick). Stir in the raspberries, blueberries or chopped cranberries (if left whole, the cranberries float to the top of the cake!) (if using). Scrape the batter into the prepared pan, level the top and sprinkle with the crumble.
- Bake for 60 to 70 minutes, until a skewer inserted in the centre comes out clean. Cool the loaf cake in the pan on a rack for 20 minutes, then turn out and let cool completely on a wire rack.
Set for the Holidays with Anna Olson, Appetite by Random House, 2018
Photos: Janis Nicolay