Salty in espresso means underextracted coffee. Many factors play there: such as grind size, pull time, tamping method, and water temp. A good espresso taste balance, you got the acidity and bitterness in sync, and give you sweet creamy taste.

Note: pourover methods usually more forgiving and give you better taste. I suggest you try those methods for your black coffee.

I'm using 60g/L, the best ratio in my opinion. I grind it using Timemore C2 and brew it using Hario Switch.