Preheat the oven to 350°F. Spray a 9x5-inch loaf pan with nonstick cooking spray and set aside.

In the bowl of a stand mixer fitted with the paddle attachment, cream together the softened butter and granulated sugar until light and fluffy, about 3 minutes. Beat in the eggs one at a time, scraping down the bowl as needed. Stir in the key lime zest, vanilla extract, and key lime juice until combined.

In a small bowl, whisk together the flour, salt, and baking soda. Gradually add the dry ingredients to the wet mixture, mixing on low speed until just combined. Fold in the sour cream until the batter is smooth and uniform.

Pour the batter into the prepared loaf pan and spread evenly. Bake for 50 minutes, or until the cake is golden brown and a toothpick inserted into the center comes out clean. Let the cake cool in the pan on a wire rack for 10 minutes, then turn out onto the rack to cool completely.

In a small bowl, whisk together the softened butter, sifted powdered sugar, and heavy cream until smooth. If the glaze is too thick, add a few more drops of cream; if too thin, add a little more powdered sugar.

Gently fold the finely chopped fresh raspberries into the glaze. Spread the glaze evenly over the completely cooled cake. Let the glaze set for about 10 minutes before slicing and serving.