Preheat oven to 350 degrees F. Line 60 to 66 (1 3/4-inch) muffin cups with paper bake cups; set aside. In a medium bowl stir together flour, baking powder, baking soda, and salt; set aside.
In a large mixing bowl beat butter with a mixer on medium to high for 30 seconds. Gradually add sugar, beating until combined. Add eggs one at a time, beating well after each addition. Alternately add flour mixture and buttermilk, beating on low after each addition just until combined. Stir in the 2 tsp. finely shredded lemon peel. Spoon batter into prepared muffin cups, filling each about two-thirds full.
Bake for 12 to 14 minutes or until a toothpick inserted near centers comes out clean. Cool in pans on wire racks for 5 minutes. Remove cupcakes from pans; cool completely on wire racks.
Prepare Lemon Cream Frosting; set aside. Spoon lemon curd into a decorating bag fitted with a small round or open star tip. Push tip into the top of each cupcake. Force some lemon curd inside cakes (or spread cupcakes tops with lemon curd). Generously pipe or spread frosting on cupcakes. To store, cover and refrigerate cupcakes.
Lemon Cream Frosting
In a large mixing bowl combine cream cheese, butter, and lemon curd. Beat with mixer on medium to high until smooth. Gradually add 3 cups of the powdered sugar, beating well. Beat in 1 Tbsp. milk. Gradually beat in another 3 cups powdered sugar. If necessary, beat in additional milk, 1 tsp. at a time, to reach spreading consistency.