01 - Preheat oven to 350°F. Grease and line three 8-inch round cake pans with parchment paper.
02 - Heat the milk until steaming without boiling. Add Earl Grey tea bags and steep for 15 minutes. Remove tea bags and let milk cool completely to room temperature.
03 - Whisk together flour, baking powder, and salt in a medium bowl until well blended.
04 - Beat softened butter and granulated 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, being careful not to overmix.
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 cooling racks to cool completely before assembling.
08 - Combine water and sugar in a small saucepan and bring to a simmer. Add tea bags and steep for 10 minutes. Discard tea bags and let syrup cool completely.
09 - Beat butter until creamy and smooth. Gradually add powdered sugar, alternating with milk, beating until fluffy and well combined. Mix in vanilla bean paste and pinch of salt until fully incorporated.
10 - Level cooled cake layers if necessary. Brush each layer generously with London Fog syrup. Spread frosting between layers and over the top and sides of the assembled cake.
11 - Decorate with edible flowers and lemon zest if desired. Refrigerate for 30 minutes before slicing to ensure clean, professional cuts.