Make Red White and Blue Poke Cake for festive gatherings; poke, pour Jell-O, and chill for colorful, crowd-pleasing slices.
Preheat (follow the box or your favorite white cake recipe) and assemble the cake batter in a rectangular 9×13 pan. Pour the smooth, pale batter into a greased rectangular metal pan, tapping gently to remove air pockets, and bake until a springy, evenly golden top forms. Let the pan rest on the painted pine surface until the cake is barely warm — the crumb should read moist and fine, with tiny air tunnels visible at the cut edge.
After removing from the oven, let the cake cool for about 15 minutes until it holds its shape but is still warm enough to accept liquid. Using a chopstick or similar narrow tool, systematically poke an evenly spaced grid of holes all over the cake surface (the holes should reach into the crumb without breaking the top crust). The surface will look dimpled and spongy, ready to accept the jellied syrups.
Dissolve the red Jell-O in ¾ cup boiling water until fully clear, then stir in ½ cup cold water; do the same separately for the blue Jell-O. Carefully pour the red gelatin liquid into every other row of holes, then pour the blue into the alternating rows so the colors sit in parallel channels throughout the cake. The liquid should sink glossy into the holes and tint the surrounding crumb vivid red and blue without pooling on the surface.

Cover the filled cake and refrigerate for at least 4 hours or overnight so the gelatin sets completely inside the crumb. When chilled, the cake will feel firm to the touch where the gelatin lives, the surface smooth, and the interior streaked with distinct wet-red and wet-blue veins.
If using whipped topping, simply spread it smoothly over the cold cake. If using heavy cream, whip 2½ cups heavy cream with 2 tablespoons powdered sugar on medium until stiff peaks form, showing glossy, structured ridges. Use an offset spatula to spread a voluminous, cloud-like white layer across the top, then chill again briefly. Slice a rectangular portion that preserves the pan’s geometry and plate it; the cut edge should reveal wet red and blue channels running through soft white crumb, topped with feathery whipped cream and optional red-and-blue sprinkles.
