Pour the boiling water into a large measuring cup. Dip the mint in the water for 5 seconds and immediately remove. Discard water and set mint aside.
Place the lemon juice and sugar in a heat prove pan over a medium heat and allow to boil.
Pour in the lemon sugar mix in a food processor add the mint and pulse until the mint is thinly chopped.
Place in a container and refrigerate over night.
Make sure all of the ingredients are at room temperature. Grease 8.3"x 3.5" loaf pan and preheat oven to 340F.
In a bowl, sift the flour and baking powder and baking soda, mix to combine.
Using a measuring cup, place the sour cream, lemon mint syrup and vanilla extract and mix to combine,
In a bowl of a standing mixer, beat the butter and sugar and lemon zest on medium speed for 4-5 minutes or until you have a light and airy mix.
Change speed to low and add the eggs one at a time waiting for each egg to fully incorporate before adding the next.
Scrap the sides and bottom of the bowl to make sure all the ingredients are fully combined.
Add the flour mixture alternating with the sour cream mixture in 4 additions, starting and finishing with the flour mixture.
Pour the batter into the greased pan and bake for 45-50 minutes or until a toothpick comes out clean from the center of the cake.
Remove form the oven and wait 10-20 minutes before removing the cake out of the pan.