01 - Preheat oven to 350°F. Grease and line three 8-inch round cake pans with parchment paper.
02 - Heat milk until steaming without boiling. Add Earl Grey tea bags and steep for 15 minutes. Remove bags and cool to room temperature.
03 - Whisk together flour, baking powder, and salt in a medium bowl.
04 - Beat butter and sugar in a large bowl until pale and fluffy, approximately 3 minutes. Add eggs one at a time, mixing thoroughly after each addition. Stir in vanilla extract and lemon zest.
05 - With mixer on low speed, add dry ingredients in three additions, alternating with cooled Earl Grey milk. Begin and end with flour mixture. Mix until just combined.
06 - Divide batter evenly among prepared pans. Smooth tops and bake for 28 to 32 minutes, or until a toothpick inserted in the center comes out clean.
07 - Let cakes cool in pans for 10 minutes, then turn out onto racks to cool completely.
08 - Bring water and sugar to a simmer in a small saucepan. Add tea bags and steep for 10 minutes. Discard bags and let syrup cool.
09 - Beat butter until creamy. Gradually add powdered sugar, alternating with milk, beating until smooth and fluffy. Mix in vanilla bean paste and salt.
10 - Level cooled cakes if needed. Brush each layer with London Fog syrup. Spread frosting between layers and over top and sides.
11 - Garnish with edible flowers and lemon zest if desired. Chill for 30 minutes before slicing for clean cuts.