01 -
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 ⅓, about 5-10 minutes. Stir constantly. Remove from heat and let cool to room temperature.
02 -
Preheat oven to 350°F / 175°C. Line the bottom and sides of two 8" (20cm) baking pans with parchment paper. Set aside.
03 -
In a medium bowl, combine flour, baking powder, and salt. Stir to combine and set aside.
04 -
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, about 2 minutes. Add 1 egg at a time and mix until fully incorporated.
05 -
Alternately add dry ingredients, milk, dry ingredients, lemon juice, ending with dry ingredients. Stir just until combined. Add vanilla and lemon zest, then stir to combine.
06 -
Divide the batter equally into the prepared pans. Bake for 28-32 minutes or until a toothpick inserted into the center comes out clean. Let the cakes cool to room temperature.
07 -
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. Sift in powdered sugar and mix until well combined. Gradually add lemon juice to achieve a creamy but firm consistency.
08 -
Trim the tops of the cakes if necessary to create flat surfaces. Cut each cake in half horizontally. Place one layer on a cake stand. Spread ¼ of the frosting over the surface, making it slightly higher at the edges to contain the filling. Layer with ⅓ of the blueberry filling. Repeat the layering process two more times, ending with the final cake layer. Lightly frost the exterior and sides with the remaining frosting.
09 -
Refrigerate the assembled cake for at least 4 hours. Store leftovers in an airtight container in the fridge for up to 4 days.