In a large bowl, beat butter and sugar until light and fluffy. Mix in ricotta, eggs, vanilla, lemon juice and lemon zest until smooth.
In another large bowl, whisk together the flour, salt, baking soda and baking powder. Add to butter mixture and mix until combined. The dough will be thick and sticky.
Refrigerate dough for 2-3 hours, or until you can shape the dough with your hands. Preheat oven to 350 degrees. Line baking sheets with parchment paper. Roll dough into walnut sized balls and place 2 inches apart on prepared cookie sheets.
Bake for 8-10 minutes, or until edges are just golden. Cool completely.
Meanwhile, make the glaze by stirring melted butter, powdered sugar, lemon juice and vanilla together in a medium bowl. Add 1/4 cup of the milk and mix until smooth. Gradually add the remaining milk, as needed, until glaze reaches desired consistency.
Spoon the glaze over the cookies, then sprinkle with colored candy sprinkles.