Preheat oven to 300°F/150°C. Grease a bundt pan. In a bowl, mix flour, spices, and zest. Set aside.
Cream butter, granulated, and brown sugar until fluffy. Add eggs one at a time, then sweet potatoes. Slowly mix in the flour mixture.
Add sour cream and vanilla. Mix gently; avoid overmixing. Pour batter into greased pan. Tap gently to remove air bubbles.
Bake at 300℉/150℃ for around 55 minutes. Check with a tester; it should come out clean. Cool the cake on a wire rack.
Melt butter in a saucepan. Add brown sugar, cream, and salt. Boil for 4-5 mins. Remove from heat, add vanilla. Let it cool.
Sift powdered sugar, add vanilla and caramel sauce. Stir until desired consistency.