
Preheat the oven to 350°F. Grease a 9x13-inch baking pan with butter or baking spray. Line it with parchment paper. (This is optional, but makes it easier to remove the cake and serve).
In the bowl of a stand mixer fitted with the whisk attachment (or a large bowl using a handheld electric mixer), combine the eggs and sugar. Beat on medium speed (level 6) for 4 to 5 minutes until the mixture is very pale yellow or off-white in color, nearly doubled in volume, and creates thick ribbons on the surface of the mixture when drizzled.
Add the butter, vanilla, and salt and beat on medium speed for 1 to 2 minutes until combined. (The mixture may look curdled. It will smooth out once the flour is folded in.)
In a medium bowl, whisk to combine 2¾ cups (330g) flour and baking powder.
Add one-half of the flour mixture to the batter and gently fold to combine. Add the milk and stir gently to combine. Fold in the remaining flour mixture.
Toss the cranberries with the remaining 2 tablespoons (15g) flour. Gently fold the cranberry mixture into the batter. (The batter will be thick. Try to distribute the berries with 5 to 6 folds, so that they don’t burst and start to streak the batter.)
Dollop the batter evenly all over the base of the prepared 9x13-inch baking pan. Spread gently into an even layer. Sprinkle the top with an additional 2 tablespoons of granulated sugar if you like.
Bake for about 50 to 55 minutes until a toothpick inserted in the center comes out clean. Let the cake cool completely in the pan before serving.