Heat your oven to 350°F and grease an 8-by-4-inch loaf pan with non-stick cooking spray. Dust one tablespoon of flour into the pan and shake to coat the bottom and the sides. Tap out any excess flour and set aside.
Add the sugar to a large bowl or the bowl of your stand mixer and zest over the lemon. Using your hands, rub the lemon zest into the sugar until very fragrant, and the sugar starts to turn a light buttery yellow colour. Add the butter and beat on high for 3 to 4 minutes until light and fluffy. Add the eggs one at a time, beating well after each addition, then beat in the vanilla extract. Stir in the sour cream and the juice from the lemon.
Whisk the remaining 2 cups of flour in a separate bowl with the baking powder and salt. Add the dry ingredients to the wet, stirring just until combined.
Transfer the batter to the prepared pan and bake for 50 minutes to 1 hour or until peaked, golden brown and a toothpick inserted into the centre comes out clean. Set aside to cool in the pan for 30 minutes, then turn it out and allow it to cool completely on a wire rack.
Trifle
For the custard, pour the milk into a medium saucepan. Add in the lemon zest and bring to a simmer over medium heat. Meanwhile, whisk together the sugar, cornstarch, and salt in a large heatproof bowl. Whisk in the egg yolks and egg.
When the milk comes to a simmer, while whisking the egg and sugar mixture constantly, slowly pour in the hot milk. Transfer the mixture to the pot and place over medium-low heat. Cook, stirring constantly, for 4 to 6 minutes or until the mixture thickens. Remove the custard from heat and whisk in the butter, vanilla, or vanilla bean paste. Strain the custard through a fine mesh sieve into a bowl to remove the bits of lemon zest and any lumps, and cover the surface directly with plastic wrap. Set aside to cool to room temperature, then transfer to the fridge for at least 2 hours to chill thoroughly.
To assemble the trifle, cut the loaf into 1-inch-thick slices. Spread each slice with thick jam and cut into bite-sized cubes. Scatter into a large glass casserole dish and top with the cooled custard. Spread into an even layer and set aside.
In a large bowl, whip the cream, sugar, and vanilla together on medium speed using a hand mixer or, if you’re athletic, whisk until the cream peaks. Spread the cream over the custard layer and dot the top with fresh raspberries.
Serve immediately or store in the fridge for up to 3 days. Enjoy!