Step 1

With the rack in the middle position, preheat the oven to 180 ºC (350 ºF).

Step 2

Butter a 20 x 10-cm (8 x 4-inch) loaf pan.

Step 3

In a bowl, beat the egg whites until stiff peaks form. Set aside.

Step 4

In another bowl, with the same beaters, cream the butter, sugar and vanilla until smooth. Add the egg yolks and continue beating. With the electric mixer on, gradually add the flour and blend until just incorporated.

Step 5

Add half of the egg whites at low speed. With a spatula, fold the remaining egg whites into the batter.

Step 6

Pour the batter into the pan and level it. Bake for 40 to 50 minutes or until a toothpick inserted in the centre of the cake comes out clean. Cool before slicing.