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 - Beat butter and sugar until light and fluffy. Add eggs one at a time, mixing well after each addition. Blend in lavender and vanilla.
04 - Alternate adding flour mixture and milk to butter mixture, beginning and ending with flour. Mix until just incorporated.
05 - Transfer batter to prepared pan. Smooth surface. Bake 25-30 minutes until toothpick inserted in center emerges clean.
06 - Simmer water, sugar, and lavender in small saucepan for 3 minutes. Strain and set aside.
07 - Let cake rest 10 minutes. If using syrup, pierce surface with small holes and brush with warm syrup. Cool completely.
08 - Whisk powdered sugar, lemon juice, and lavender until smooth. Drizzle over cooled cake.
09 - Allow glaze to set before slicing and serving.