Preheat your oven to 350ºF (177ºC) and grease three 6-inch (or two 8-inch) round cake pans, lining the bottoms with parchment paper.

In a large mixing bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt.

In a measuring cup, whisk together the whole milk and freshly squeezed lemon juice, letting it sit for about 5 minutes.

In a stand mixer, combine the lemon zest and granulated sugar, then add the unsalted butter and beat until light and fluffy.

Gradually mix in the vegetable oil, followed by eggs one at a time, and vanilla extract, scraping down the bowl as needed.

With the mixer on low, combine half of the dry ingredients, then the lemon milk, then the remaining dry ingredients until just combined.

Toss 2/3 of the fresh blueberries with a small amount of flour and gently fold into the batter.

Divide the batter between the prepared pans and top with reserved blueberries.

Bake for 30-35 minutes until a toothpick inserted comes out clean.

Cool the cakes in the pans for 5 minutes before transferring them to a wire rack.

For the frosting, beat the softened unsalted butter until smooth, then gradually add powdered sugar and lemon juice, finishing with the cream cheese.

Level the cake layers if needed, assemble by alternating layers and frosting in between, chilling the cake to set.

Apply a final layer of frosting, decorate with blueberries and lemon slices.