Preheat oven to 350°F. Pour boiling water over tea bag and steep 3 minutes. Remove tea bag and allow tea to cool. Sift together flour, baking soda, baking powder and salt; set aside. In a liquid measure, combine green tea, lemon juice and zest, and buttermilk; set aside. In a mixing bowl, cream butter until fluffy. Add agave; mix well. Add eggs, one at a time. Add half of the reserved dry ingredients to the butter mixture; mix on low until just combined. With mixer running on low, slowly add the lemon tea mixture. Add remaining dry ingredients until just combined. Fill paper-lined muffin tins 2/3 full. Bake 18-22 minutes, or until a toothpick inserted in center of a muffin comes out clean. Remove to wire rack; cool. Frost and decorate with Agave Lemon Frosting and Candied Lemon Slices, if desired.

AGAVE LEMON FROSTING and CANDIED LEMON SLICES:
Preheat oven to 200°F. Pour agave in a small skillet and add lemon slices in a single layer. Bring to a boil over medium heat. Reduce heat and simmer for 15 to 20 minutes, turning slices occasionally. Remove from heat; reserve syrup. Place slices on a parchment-lined cookie sheet and bake 10 minutes. Turn slices and bake an additional 10 minutes or until slices are dry. In a mixing bowl, cream butter until light and fluffy. Add 2 cups of powdered sugar; mix well. Slowly add cooled reserved syrup and lemon juice and zest; mix well. Add remaining powdered sugar; beat well.