Lemon Blueberry Cake | Also The Crumbs Please

Ingredients
Blueberry filling
4 heaping cups blueberries, fresh or thawed (600g)
1 cup granulated white sugar (200g)
juice of 2 lemons
Lemon cake
3 cups all-purpose flour (360g)
1 tbsp baking powder
1/2 tsp salt
1/2 cup unsalted butter, room temperature (113g)
1/2 cup vegetable oil (120ml)
1+3/4 cups granulated white sugar (350g)
3 large eggs
1 cup milk (240ml)
1/2 cup freshly squeezed lemon juice (120ml)
2 vanilla beans* (or 2 tsp vanilla extract)
1 tbsp lemon zest
Lemon cream cheese frosting
1 cup unsalted butter, room temperature (226g)
1 cup cream cheese, room temperature (8oz / 226g)
2 cups powdered sugar (240g)
1-2 tbsp freshly squeezed lemon juice (15-30ml)

Instructions
Make the blueberry filling: In a medium saucepan, combine all ingredients and bring to a simmer over medium heat. Cook until the blueberries are soft and the sauce has thickened up and is reduced by 1/3, about 5-10 minutes. Stir constantly. Remove from heat and let cool to room temperature. It will thicken as it cools.

Preheat oven to 350°F / 175°C. Line the bottom and the sides of two 8″ (20cm) baking pans with parchment paper. Set aside.

Make the lemon cake: In a medium bowl combine flour, baking powder, and salt and stir to combine. Set aside. In a large mixing bowl with a stand or handheld mixer fitted with a whisk or paddle attachment, beat butter, oil, and sugar on medium speed until creamy for about 2 minutes. Add 1 egg at the time and mix until fully incorporated. Alternately add dry ingredients, milk, dry ingredients, lemon juice, and end with dry ingredients. Stir just until combined. Add vanilla* and lemon zest and stir to combine. ** Divide batter into the two prepared baking pans equally. Bake for 28-32 minutes or until a toothpick in the center comes out clean. Don’t overbake or the cake will be dry. Let cool to room temperature.

Make the lemon cream cheese frosting: In a large mixing bowl, using a handheld or stand mixer fitted with a paddle attachment, whisk butter on medium speed until creamy. Add cream cheese and whisk until smooth and combined. Sift in powdered sugar and stir until well combined and creamy. Add 1 tbsp lemon juice at the time and stir until smooth and creamy. The frosting should be creamy but firm enough to frost the cake with an offset spatula. If the frosting is too soft, add more powdered sugar. If the frosting is too firm, add more lemon juice. Watch the video and the pictures above to see the consistency of the frosting.

Assemble the cake: Cut a thin layer off the tops of your cakes to create a flat surface if needed. Then cut each cake in half horizontally. Place one cake layer on a cake stand or serving plate. Spread 1/4 of the frosting over the cake. The frosting should be higher around the edges that it holds the blueberry filling inside the cake (watch the video and the step-by-step photos for better understanding). Layer with 1/3 of the blueberry filling (where the frosting is lower). Repeat two more times. Place last cake layer on top and lightly frost the outside and the sides of the cake with the remaining frosting. Chill 4 hours in the fridge. Store leftovers in an airtight container in the fridge up to 4 days.