Preheat oven to 350 degrees.
In a food processor, process pistachios until finely ground. Set aside
In a large bowl, with mixer at low speed, combine sugar and butter until blended. Increase speed to high and beat about 5 minutes, until light and fluffy.
At medium speed, beat in ricotta, vanilla, ground pistachio and eggs until combined.
Reduce speed to low and add flour, baking powder and salt; beat until dough comes together.
Using a scoop, drop cookies about 2 inches apart on large ungreased cookie sheet.
BAke for 15 minutes or until cookies are very lightly golden. Cookies will be soft. Let cool on wire racks.