01 - Preheat oven to 350°F. Grease and line three 8-inch round cake pans with parchment paper.
02 - In a small saucepan, heat the milk until steaming but not boiling. Remove from heat. Add Earl Grey tea bags and lavender; cover and steep for 15 minutes. Strain and cool to room temperature.
03 - In a bowl, whisk together flour, baking powder, and salt.
04 - In a large bowl, cream butter and sugar with an electric mixer until light and fluffy (about 3-4 minutes).
05 - Beat in eggs, one at a time, mixing well after each addition. Add vanilla extract.
06 - With the mixer on low, add flour mixture in three parts, alternating with the cooled tea-infused milk, beginning and ending with flour. Mix until just combined.
07 - Divide batter evenly among the prepared pans. Smooth the tops with a spatula.
08 - Bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
09 - Let cakes cool in pans for 10 minutes, then turn out onto wire racks to cool completely.
10 - Beat butter until creamy. Gradually add powdered sugar, milk, vanilla bean paste, and salt; beat until fluffy and smooth.
11 - To assemble, place one cake layer on a serving plate. Spread with frosting. Repeat with remaining layers. Frost the top and sides of the cake.
12 - Decorate with dried lavender buds and lemon zest if desired.