Cookie Dough: Using an electric mixer, cream together sugar and butter in a medium size mixing bowl. Beat at medium speed, scraping bowl often, until creamy. Add sour cream, eggs, lemon zest, lemon extract and almond extract. Continue beating until fully combined.
In a separate bowl, use a whisk to sift together flour, baking powder and salt. With the mixer on low speed, gradually add to the wet ingredients beating until well mixed. Stop and scrape the sides of the bowl periodically.
Cover and chill dough for 30 minutes.
Bake: Preheat oven to 350°F. Line 2 baking sheets with parchment paper. Set aside.
Use a small scoop to divide dough into equal portions, rolling into 1 1/2 inch balls. Place onto baking sheet at least 2 inches apart. (If baking in batches, keep dough chilled between.)
Bake for 12-14 minutes or just until lightly golden. Cool on the pan for 5 minutes then remove to a cooling rack to cool completely.
Frosting: In a bowl, combine powdered sugar, lemon juice, heavy cream and zest. Mix until creamy, adding additional cream as needed to spreading consistency.
Frost each cookie and sprinkle with additional lemon zest, if desired.
Store at room temperature or chilled in an airtight container in a single layer for up to 5 days. If stacking, place wax paper between cookies.