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 cranberries and stir to mix throughout.
Spread in a buttered 9×13 pan. Bake for 40-50 minutes, or until very lightly browned and a toothpick inserted near the center of the cake comes out clean. (I baked mine for 43 minutes.) 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 at a party. Enjoy!