How to make
Beat the condensed milk with the softened butter and add the eggs one by one while constantly beating with a mixer. Bubbles should form and the mixture should become as fluffy as possible.
Add the oil, vanilla, finely grated lemon peel and gradually integrate the flour previously sifted with the baking powder. If you use condensed milk, which is thinner and not as sweet, you should also add a spoonful or two of powdered sugar (I sometimes have to add sugar).
Again, how much flour it will take depends on the milk and its thickness. So put it in portions and mix smoothly until you get the perfect sponge cake batter consistency.
Pour the mixture into a greased and buttered sponge cake tin. Spread the blueberries on top and press them down slightly.
Bake in an oven heated to 360°F (180°C) for about 40 minutes or until it is fully baked.
Cool the finished sponge cake with condensed milk and fresh blueberries on a wire rack, sprinkle with powdered sugar and serve with a cup of coffee.