01 - Preheat the 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 in a large bowl until light and fluffy. Add eggs one at a time, mixing well after each addition. Blend in lavender and vanilla extract.
04 - Alternately add the flour mixture and milk to the butter mixture, beginning and ending with flour. Mix until just combined.
05 - Pour batter into the prepared pan and smooth the top evenly. Bake for 25-30 minutes or until a toothpick inserted in the center comes out clean.
06 - Simmer water, sugar, and lavender in a small saucepan for 3 minutes while the cake bakes. Strain and set aside.
07 - Let the cake cool in the pan for 10 minutes. If using syrup, poke small holes in the surface and brush lightly with warm syrup. Cool completely.
08 - Mix powdered sugar with lemon juice and lavender until smooth. Drizzle over the completely cooled cake and let set before slicing and serving.