1. Preheat oven to 350°F (177°C). Grease three 9-inch or 8-inch round cake pans (8-inch pans produce thicker cakes), line bottom with parchment paper, then grease the parchment paper. Parchment paper helps the cakes seamlessly release from the pans.
2. Make the cake: Using a handheld or stand mixer with a paddle attachment, beat the butter on high until creamy – about 1 minute. Add granulated and brown sugars and beat on medium-high speed until creamed, about 2-3 minutes. Add eggs and vanilla. Beat on medium speed until everything is completely combined, about 2 full minutes. Scrape down the sides and bottom of the bowl as needed.
3. In a large bowl, whisk together the flour, baking powder, and salt. Slowly add the dry ingredients to the wet ingredients. Beat on low speed for 5 seconds, then beat in the milk, lemon zest, and lemon juice *just* until combined. Toss the blueberries with 1 Tablespoon of flour and gently fold into the batter. Batter is extremely thick. Do not over-mix. Over-mixing will lead to a tough, dense textured crumb.
4. Spoon batter evenly into prepared cake pans. Bake for about 21-25 minutes or until a toothpick inserted in the center comes out clean. (8 inch cakes take closer to 25 minutes.) Remove from the oven and allow to cool completely in the pan before assembling and frosting.
5. Make the frosting: Using a handheld or stand mixer with a paddle attachment, beat cream cheese and butter together on medium speed until no lumps remain, about 3 full minutes. Add confectioners’ sugar, 1 Tablespoon cream, vanilla extract, and salt with the mixer running on low. Turn mixer to high speed and beat for 3 minutes. Add 1 more Tablespoon of cream to thin out, if desired.
6. Assemble and frost: First, using a large serrated knife, trim the tops off the cake layers to create a flat surface. Place 1 layer on your cake stand. Evenly cover the top with cream cheese frosting. Top with 2nd layer, more frosting, then the third layer. Top with frosting and spread around the sides. The recipe doesn’t make a ton of frosting, just enough for a light frost. Top with blueberries or lemon garnish if desired. Refrigerate for at least 45 minutes before cutting or else the cake may fall apart as you cut.
7. Cover leftover cake tightly and store in the refrigerator for up to 5 days.