Blueberry Poke Cake

1 . Stage

Preheat the oven to 350 degrees F (175 degrees C). Grease and lightly flour a 9x13-inch baking pan.

2 . Stage

Blend cake mix plus extender, 1 1/4 cups water, egg whites, and oil together in a bowl using an electric mixer until just moistened. Pour batter into the prepared pan.

3 . Stage

Bake in the preheated oven until a toothpick inserted into the center of the cake comes out clean, 32 to 26 minutes.

4 . Stage

While cake is baking, stir sugar and cornstarch together in a small saucepan over medium heat. Add 1 cup water and bring to a boil, stirring constantly. Add blueberries and lemon juice; cook and stir until blueberries burst and sauce turns a deep purple color, about 10 minutes. Gently mash any berries that did not burst. Remove from heat and let cool until cake is ready.

5 . Stage

Transfer cake to a cooling rack and let cool to room temperature, at least 25 minutes.

6 . Stage

Poke holes into the cake about 1 inch apart using the handle of a wooden spoon. Slowly pour the warm blueberry sauce over cake. Refrigerate until cool before slicing.