BA’s Best Carrot Cake

Name: BA’s Best Carrot Cake
Cuisine: European
Ingredients: Nonstick vegetable oil spray; ½ cup golden raisins (optional); 3 tablespoons dark rum (optional); 1 cup chopped walnuts; 1 pound carrots, peeled, coarsely grated; 1 cup buttermilk, room temperature; 2½ cups all-purpose flour; 2 teaspoons ground cinnamon; 2 teaspoons ground ginger; ½ teaspoon freshly grated nutmeg; 2 teaspoons baking powder; 1½ teaspoons kosher salt; ¾ teaspoon baking soda; 4 large eggs, room temperature; 1 cup granulated sugar; ¾ cup (packed) dark brown sugar; 2 teaspoons vanilla extract; ¾ cup vegetable oil; 12 ounces cream cheese, room temperature; ¾ cup (1½ sticks) unsalted butter, room temperature; 1 teaspoon vanilla extract; Generous pinch of kosher salt; 4 cups powdered sugar; Candied Carrot Coins (optional)