Preheat the oven to 350 degrees F. Butter and flour a 9-inch round cake pan and line it parchment paper. Crack the eggs and place them in a small bowl. Place the flour, salt, baking powder, and baking soda in medium-sized bowl and whisk together for 30 seconds to thoroughly.
Place the granulated sugar, the brown sugar, the butter, the cinnamon, ginger and nutmeg in a large bowl. Start the mixer on low speed. As soon as the sugar, butter and spices start to come together increase the speed to medium high and beat until the batter is lighter in color, smoother in texture and fluffier, about 4 minutes. Scrape the sides and bottom of the bowl
Add the mashed sweet potato and mix on medium high for 1 minute, until it is thoroughly combined. There should be small pieces of sweet potato and the batter should be light orange. Add the eggs one at time, beating the batter after each addition until each egg is thoroughly combined into the batter. Scrape the sides and bottoms of the bowl.
Add half of the flour mixture and mix on low speed until the flour is incorporated. Add all of the sour cream and mix on low speed until thoroughly combined. Add the remaining flour and mix on low speed until combined. Scrape the sides and bottom of the bowl. Add the bourbon and mix on low speed until thoroughly combined.
Scrape the cake into the prepared cake pan. Use an offset spatula to smooth and level the batter. Bake the cake 35-40 minutes, but start checking for doneness at 30 minutes. Use a cake tester or a toothpick to test the doneness. When the cake tester is inserted in the center of the cake and removed there should be no batter clinging to the tester. If you have an instant read thermometer you can check the temperate at center of the cake. It will be about 200 degrees F.
Remove the cake from the over. Allow it cool in the pan for 10 minutes and then invert it onto a lightly oiled cake rack to finished cooling.
The unfrosted cake can sit a room temperature to up to 3 days.