Preheat oven to 350 degrees. Beat eggs with sugar until light and thick, about 5-7 minutes. Mix in softened butter and vanilla. Stir in flour and cranberries until just combined. Spread batter into a buttered 9x13 inch pan. Bake for 40-50 minutes until lightly golden and a toothpick inserted in the center comes out clean. Let cool before serving.