Preheat the oven to 350°F and grease a large ramekin with butter.
In a medium bowl, use a fork or rubber spatula to cream together the softened butter and sugar. Mix in the egg yolk and vanilla to combine then mix in the lemon juice and zest before finally mixing in the sour cream.
Add the flour, baking powder, and salt and stir until just combined. Do not over mix and the batter will be thick.
Pour into the greased ramekin and spread into an even layer.
Bake in the preheated oven for 25-30 minutes. The pound cake is done when a toothpick inserted in the center comes out clean with only a few moist crumbs.
While the cake cools slightly, mix together the icing ingredients.
Remove the pound cake from the ramekin while still warm and pour over the icing.
