01 - Preheat oven to 350°F. Grease and flour an 8-inch round cake pan.
02 - Whisk together flour, baking powder, and salt in a bowl. Set aside.
03 - In a large bowl, beat butter and sugar until light and fluffy. Add eggs one at a time, mixing well after each addition. Stir in lavender and vanilla.
04 - Alternately add flour mixture and milk to butter mixture, beginning and ending with flour. Mix until just combined.
05 - Pour batter into prepared pan. Smooth top. Bake for 25-30 minutes or until toothpick inserted in center comes out clean.
06 - While cake bakes, simmer water, sugar, and lavender in small saucepan for 3 minutes. Strain and set aside.
07 - Let cake cool for 10 minutes. Poke small holes in cake and lightly brush with warm syrup if using. Cool completely.
08 - Mix powdered sugar with lemon juice and lavender until smooth. Drizzle over cooled cake. Let set before slicing.