Preheat the oven to 350°F (175°C). Grease and flour a 10- or 12-cup Bundt pan.
Whisk together the flour, baking powder, baking soda, and salt. Set aside.
In a large mixing bowl, cream together the butter and granulated sugar until light and fluffy.
Add the eggs one at a time, beating well after each addition. Stir in the limoncello and lemon zest until well combined.
Gradually add the dry ingredients to the butter mixture in three portions, alternating with two portions of the sour cream. Mix until just combined.
Pour the batter into the prepared pan pan and smooth the top. Bake for 55-60 minutes, or until a pick or cake tester inserted into the center comes out clean.
Let the cake cool in the pan for 10 minutes, then invert onto a wire rack to cool completely.
To make the glaze:
In a small bowl, whisk together the confectioners' sugar, 1 tablespoon (15ml) of limoncello, and lemon juice until smooth. Add more limoncello, a small amount at a time, until the glaze is the desired consistency.
Drizzle the glaze over the cooled cake.
Notes
Store in an airtight container at room temperature up to 3 days.