Preheat the oven to 350ºF/177ºF and prepare three 6-inch or two 8-inch cake pans by spraying the sides with cooking spray and fitting a parchment paper circle to the bottoms.

In a large bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside. In a liquid measuring cup, whisk together the milk and lemon juice and set aside.

Using a stand mixer fitted with the paddle attachment, mix together the sugar and lemon zest until fragrant and well combined, about 1 minute. Add the butter and cream it together with the lemon-sugar mixture on medium speed until light and fluffy, about 2 minutes. Add the vegetable oil and beat until combined, light and creamy, about 3 minutes. Scrape down the bowl and paddle as needed.

With the mixer on low speed, add the eggs one at a time and mix until combined. Add the vanilla, then turn the mixer to medium speed and beat for one minute.

Turn the mixer off and add the flour mixture all at once. Mix on low speed until just combined, then slowly pour in the lemon milk mixture. Mix until just combined, about 30 seconds.

Coat the blueberries in 2 teaspoon flour, then reserve about ⅓ of them and set aside. Use a rubber spatula to fold the remaining ⅔ into the lemon cake batter, then divide the batter evenly between the prepared cake pans. Now take the reserved blueberries and divide them between the pans, gently pressing them into the tops. Bake for 30-35 minutes, until a toothpick inserted into the centers comes out clean or with a few moist crumbs. Cool for 5 minutes before removing the cakes from the pans. Transfer the cake layers to a wire rack to cool completely to room temperature.

In the bowl of a stand mixer fitted with the paddle attachment, beat the butter on medium-high speed until light and creamy, about 5 minutes, scraping down the bowl and paddle as needed.

Add about ⅓ of the powdered sugar and mix on low speed until combined, then add the lemon juice and continue mixing on low speed. Add the rest of the powdered sugar until combined. It will look pretty crumbly and thick, but don't worry! It will come together after the next step.

Add the cream cheese and salt and mix on medium speed until fully combined and smooth (no lumps), about 2-3 minutes, scraping down the bowl and paddle as needed.

Once the cake layers have cooled completely, level them to your desired height. Fill and stack the cake layers with lemon cream cheese buttercream, then crumb coat the cake with more lemon cream cheese buttercream. Refrigerate the crumb coated cake for at least 30 minutes to let the frosting firm up.

To create the design pictured, use the lemon cream cheese buttercream to frost a semi-naked finish on the cake. Add the remaining lemon cream cheese buttercream into a piping bag fitted with Wilton Tip 4B, then pipe a braided border (a series of overlapping diagonal shells) onto the top edge of the cake. Garnish the braided border with fresh blueberries and slivers of a lemon slice.