Luscious Lemon Cake with Melting Custard Filling (Ready in 15 Minutes Prep!)

Instructions:

In a saucepan, whisk together the egg, sugar, salt, and cornstarch until smooth.
Gradually whisk in the milk, ensuring no lumps form.
Add the lemon zest and juice of half a lemon.
Cook over medium heat, stirring constantly, until the mixture thickens and boils.
Remove from heat and stir in the butter until melted. Let cool completely.
Prepare the Lemon Cake Batter (4 Minutes):

In a large bowl, beat the eggs, sugar, and salt until light and fluffy.
Beat in the vanilla sugar (or vanilla extract), vegetable oil, and sour cream.
Combine Dry and Wet Ingredients (2 Minutes):

In a separate bowl, whisk together the flour and baking powder.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Stir in the remaining lemon juice.
Assemble and Bake (7 Minutes):

Preheat your oven to 180°C (356°F). Grease your casserole dish.
Pour half of the cake batter into the prepared dish.
Spread the cooled lemon custard filling evenly over the batter.
Pour the remaining cake batter over the custard filling.
Garnish with toasted almonds (optional).
Bake for 40 minutes, or until a toothpick inserted into the center comes out clean.
Serve:

Let the cake cool slightly before dusting with powdered sugar (optional) and serving.
Advanced Techniques:

Folding vs. Mixing: When incorporating the dry ingredients into the wet batter, use a folding motion with a spatula to maintain air pockets in the batter. This will contribute to the light and fluffy texture of the cake.
Don’t Overmix: Once the dry ingredients are just incorporated, stop mixing. Overmixing can lead to a tough and dense cake.
Flavor Twists:

Lemon Glaze: For an extra burst of lemon flavor, you can drizzle a simple lemon glaze over the cooled cake. To make a glaze, whisk together powdered sugar, lemon juice, and a touch of milk until smooth.
Lemon Extract: If you don’t have fresh lemons for the zest and juice, you can substitute with 1 teaspoon of lemon extract for the zest and 2 teaspoons of lemon extract for the juice. However, using fresh lemons will provide a brighter and more intense lemon flavor.
Poppy Seeds: Add a tablespoon of poppy seeds to the cake batter for a subtle nutty flavor and textural contrast.
Lemon Curd Option: If you have leftover lemon curd, you can use it instead of making the custard filling. Spread a layer of lemon curd over the batter before adding the remaining batter and baking as instructed.