Preheat oven to 350 F.

Beat eggs with 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, so do not skip this step.)

Add butter and vanilla and beat for two more minutes. Stir in flour just until combined. Add the cranberries and stir to mix throughout.

Spread into a greased 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. Let cool completely before cutting into small squares.