Preheat the oven. Line a rectangular baking dish with baking paper and grease with non-stick cooking spray. Beat the egg whites until just stiff, but not dry. Now use the same mixer on high speed to beat the egg yolks and sugar together for 10 minutes. Add the oil and coffee, followed by the dry ingredients, and fold together until just combined. Finally, fold the egg whites through the batter and pour it into the prepared dish. Bake the cake until a skewer comes out clean (about 45 minutes).
1. Allow the cake to cool completely. With the handle of a wooden spoon, poke holes all over the surface. (Or press a hole into each square, according to how you’ll cut it.)
2. Pipe or spoon jam into each hole.