[German > English] Short recipe translation help please

Hi,

I am looking for help translating this recipe written from Oma. My family has craved this cake called “Ein Ei” for decades, thinking that the recipe was lost forever after she passed away in the 1980s (I was young and never knew this cake). I just found a recipe with this name buried with hundreds of other German recipes discovered in a box at my grandmother’s house and would love to make it for my family!
If helps, she was from a small town near Stuttgart and moved to Canada in the 1950s. I’ve been told many of her recipes include some Yugoslavian terms (she lived there for a while when younger) and other things that may not be standard “German”.

My food-related German isn't terrible, but I’m not sure of a few of the words and notations. And it doesn’t seem like there’s much information on the instructions beyond the ingredients. Any help is greatly appreciated!

What I’ve figured out so far is:

Ein-ei Kuchen (One Egg Cake)

  • 4-5 (Cap? Cups?) Flour
  • 3 egg yolks, 1 whole egg
  • 5 TBSP sour cream
  • 1 Tsp salt, 2 (tsp?) baking powder or baking soda (though I usually see this word as “backpulver”, and I can’t tell the difference between baking powder and baking soda in these recipes)
  • 1/2 (cap? Cups?) milk lemon zest (missing a measurement on lemon zest?)
  • 1 pf (pound?) lard, bake immediately
  • Not in fridge?

https://preview.redd.it/f8s5wt84dvde1.jpg?width=3024&format=pjpg&auto=webp&s=c4b3931df63a40286031e731b99fcfba79f4fa5e