Preheat oven to 350 degrees. With a mixer, beat the eggs with the sugar until slightly thickened and light in color, about 5-7 minutes. The mixture should almost double in size. The eggs work as your leavening agent in this recipe, so do not skip this step. This mixture should form a ribbon when you lift the beaters out of the bowl. Add the butter and vanilla; mix two more minutes. Stir in the flour until just combined. Add the blueberries and stir by hand to mix throughout.

Spread in a buttered 9x13 pan. Bake for 40-50 minutes, or until very lightly browned and a toothpick inserted near the center of the cake comes out clean. (43-45 minutes works great for my oven.) Let cool completely before cutting into small slices. I cut mine into fairly small pieces, about 1"x2", so that they could be easily eaten by hand. Enjoy!