Preheat your oven to 350°F and grab a 9x13-inch baking pan. Line it with parchment paper or just grease it generously—either way works fine. You'll want the oven fully heated before the batter goes in so it rises evenly.

Cream together the butter and sugar in a large mixing bowl until it's light and fluffy, about 2-3 minutes. Add the eggs one at a time, beating after each one so they incorporate smoothly. This step matters because it creates tiny air bubbles that make your cake fluffy instead of dense.

Mix the flour, baking powder, salt, and lemon zest in a separate bowl. Alternate adding the dry ingredients and milk to your butter mixture, starting and ending with the dry stuff. Begin with about 1/3 of the flour mixture, then half the milk, then another 1/3 of flour, the rest of milk, and finish with the final flour portion.

Pour the batter into your prepared pan and bake for 28-30 minutes until a toothpick inserted in the center comes out clean. The cake should look golden around the edges but still slightly soft in the middle—don't overbake or it gets rubbery. I always check mine at minute 28 because every oven runs a little differently.

Let the cake cool completely in the pan, then turn it out onto a wire rack or your serving platter. This takes about an hour at room temperature, but you can speed it up by sticking it in the fridge for 20 minutes if you're in a time crunch. Mine always sticks a little to the pan and that's totally fine—just use a thin spatula to gently release it.

Once cooled, frost the entire top with a simple buttercream or whipped frosting (store-bought frosting is totally acceptable here, no judgment). Arrange fresh strawberry halves in three horizontal stripes across the width, then fill the top left corner with blueberries in a scattered pattern. Step back and admire your american flag cake family easy recipe before anyone demolishes it.