Preheat the oven to 350 degrees Fahrenheit. Butter and flour one Breadwinner loaf pan.
In a large bowl, whisk together the flour, baking powder, and salt. In a two-cup measuring cup, whisk together the sour cream and the milk.
With an electric mixer on medium speed, beat the butter and sugar in a large bowl until pale and fluffy, about 3 minutes. Add the egg, one at a time, scraping down the sides of the bowl occasionally. Beat in the vanilla.
Alternate adding the flour mixture and the sour cream mixture to the egg mixture, starting and ending with the flour mixture.
Transfer the batter to Breadwinner and smooth the top. Sprinkle the top with a generous amount of sanding sugar.
Bake until a toothpick inserted into the center comes out clean, 55 to 65 minutes. Transfer the pan to a wire rack to cool for 1 hour, then remove the cake from the pan to cool completely.
Meanwhile, prepare the caramel. In Saucy, bring the cream, cinnamon, cardamom, and ginger to a boil. Remove from the heat and stir in the tea bags. Set aside and let steep for 20 minutes. Strain the cream and discard the solids. You should now have 1/2 cup spiced heavy cream.
Sprinkle the sugar in an even layer over the bottom of Deep Cut. Heat the pan over medium-high heat, without stirring (although you can gently swirl the pan, if necessary) until the caramel is medium amber in color, 5 to 6 minutes. Add the butter, stirring constantly, then carefully add the cream. Be careful: It will steam and sputter. Add a pinch of salt. Cook for another minute or two, stirring, until the caramel is smooth and has thickened slightly. (It will continue to thicken as it cools.)
Serve slices of cake with a dollop of cream and a drizzle of caramel.