My espresso tastes sour!
A well-known problem that most of you have experienced at least once.
Depending on the variety and roast, there are beans that bring strong fruit acids which can be desired and emphasized with the right technique. However, most espressos are in the medium to dark roast range. Even in this case, a slight acidity can be very pleasant. But, if the espresso shot does only taste sour, there are several approaches to influence the whole result.