Step 1Four hours or the night before baking the cake, stir brown sugar and tea together in medium nonaluminum mixing bowl to dissolve sugar. Stir in golden raisins, dark raisins, currants, orange peel, brandy and orange oil. Cover with plastic wrap and set aside.
Step 2Mix together flour, baking powder, cinnamon, nutmeg, salt and lemon and orange zests to blend. Add to fruit mixture. Stir in egg and melted butter, then mix to make a loose batter.
Step 3Spray 8x4-inch loaf pan with cooking spray. Pour batter into pan. Bake at 325 degrees until dark brown, loaf springs back when touched lightly and toothpick inserted in middle comes out clean, about 1 to 1 1/2 hours. Cover top with foil and reduce heat to 300 degrees if top is getting too dark. Cool in pan 15 minutes, then turn out and cool on rack. Wrap well.