Preheat your oven to 350°F (175°C) and line a muffin pan with cupcake liners.

In a mixing bowl, cream together softened unsalted butter and granulated sugar until light and fluffy.

Incorporate the large eggs, mixing well after each addition until the batter is smooth.

Add key lime juice and vanilla extract, blending on low speed.

Whisk together flour, baking powder, baking soda, and salt in a separate bowl.

Gradually combine dry ingredients with the wet mixture, alternating with sour cream until just mixed.

Fill each cupcake liner about two-thirds full with batter and bake for 18-20 minutes.

Allow cupcakes to cool in the pan for 5 minutes before transferring to a wire rack.

Prepare the frosting by beating together cream cheese, powdered sugar, key lime juice, and vanilla until smooth.

Once cooled, frost each cupcake and garnish with lime zest or a lime slice if desired.