Place three tea bags in boiling water. Let steep for 3-5 minutes. Remove tea bags and let tea cool.
Preheat oven to 350 degrees. Spray a loaf pan with nonstick cooking spray. Set aside.
In a large bowl, combine flour, baking powder, baking soda, salt and all spice. Stir to combine.
In a separate bowl, combine sugar, buttermilk, walnuts, butter, oil, marmalade, eggs and 3 Tbsp of tea from step 1. Stir well.
Stir wet ingredients into dry ingredients. Mix until just combined. Pour into prepared loaf pan.
Bake in preheated oven for 40-45 minutes or until toothpick inserted comes out clean. Let cook in pan for 5-10 minutes and then cool completely on wire rack.
For glaze: stir together powdered sugar and 2 tsp tea until smooth. Drizzle on cooled bread.