@Mike Drone
So I couldn't find the hand-written recipe that my mother followed. It's around here somewhere, and if I find it in the next day or so, I'll post it, mostly because that's the one that I know is tried and true.
Most of the recipes vary in number of eggs used, and as I said, many of them online call for the eggs to be beaten together, but that's if you want the denser version of it. If you want the nice fluffy version, the the yolks and whites are done separately. The key is to make sure the whites are folded *very* gently into the yolk/sugar/flour mixture, a little bit at a time.
Here's a picture of the recipe from my Portuguese cook book (don't worry, it's in English

):
Clearly this was written for a more 'old-school' sort of kitchen - we always used the Kitchen Aid to beat the eggs, not a whisk. None of us had the stamina to beat egg whites by hand!
And here's a link to a similar recipe, with slightly different proportions but similar procedures:
Portuguese Sponge Cake - Pao de Lo | DianasDesserts.com
I personally would go with the proportions in the image - the recipe in the link calls for more sugar and flour, and I think that makes it too sweet. It's one of the things I liked about this cake, that it's not super sweet.
Also, none of them mention the zest. My mother would usually use the zest from one whole orange and add it to the yolks. We also tended to use vanilla extract rather than almond as another variation.
This cake was a staple for Christmas, and for a few years, she would make this recipe as a sheet cake instead of a round tube cake. There was homemade vanilla and chocolate pudding between layers, and homemade whipped cream as the frosting. Sometimes sliced strawberries also made it between layers.
Sooooooo want cake now!!
