Preheat your oven to 350°F (175°C) and grease a round cake pan.
In a large bowl, cream the softened butter and sugar together until light and fluffy.
Add the eggs one at a time, mixing well after each addition.
Stir in the key lime juice and lime zest until combined.
In a separate bowl, whisk together the flour, baking powder, baking soda, and salt.
Gradually add the dry ingredients to the wet mixture, mixing until just combined.
Pour the batter into the prepared cake pan and smooth the top.
Bake for 25-30 minutes or until a toothpick inserted in the center comes out clean.
Allow the cake to cool in the pan for 10 minutes, then transfer it to a wire rack to cool completely.
Prepare the frosting by whipping the cream and mixing it with cream cheese and powdered sugar until smooth.