Preheat your oven to 350°F and line a 9x13-inch pan with parchment paper. I do this first because a cold oven is my biggest 4th of july flag cake crowd mistake—the batter starts setting before heat reaches the center, creating uneven crumb texture.

Cream butter and sugar together for exactly 3 minutes until the mixture looks pale and slightly fluffy. This step matters because you're incorporating tiny air pockets that will expand in the oven, creating a tender crumb instead of a dense brick.

Add eggs one at a time, beating for 30 seconds between each addition until they fully incorporate. I used to skip this step and dump all three eggs at once—the result was a gritty, separated batter that never recovered, so trust the process here.

Whisk together flour, baking powder, and salt in a separate bowl, then alternate adding this dry mixture and whole milk to your butter mixture, starting and ending with flour. The reason for alternating is that milk prevents the flour from forming tough gluten strings, which keeps your 4th of july flag cake crowd recipe impossibly soft.

Divide your batter into three equal parts in separate bowls, then stir strawberry puree into one portion, blueberry puree into another, and leave the third plain white. This is where the magic happens—you're creating three distinct colored layers that will stack into a flag pattern.

Pour the white batter into your prepared pan and smooth the top, then layer the strawberry batter on top, followed by the blueberry batter on top of that. Bake for 48-52 minutes until a toothpick inserted in the center comes out with just a few crumbs clinging to it—not completely dry, because that's when overBaking happens.

Cool the cake completely in the pan for 20 minutes, then invert onto a wire rack and cool for another hour before frosting. I learned the hard way that frosting a warm cake causes the whipped cream to melt and slide off, so patience here prevents frustration later.

Whip the cream with powdered sugar, lemon juice, butterfly pea flower powder, and vanilla powder until stiff peaks form, then spread generously over the cooled cake. Top with fresh berries arranged in a flag pattern—strawberries on the top third, blueberries scattered over the top-left corner to mimic stars.