Preheat oven to 325°F. Thoroughly coat 2 (6-cup) mini cake trays with baking spray. Whisk together flour, salt, and baking soda.

In a stand mixer, beat butter, sugars, and lemon zest on medium speed until light and fluffy, about 3 minutes. Add eggs, 1 at a time, beating well after each.

In a small bowl, whisk together sour cream, milk, and vanilla. With the mixer on low, gradually add the flour mixture and sour cream mixture in alternating batches, beginning and ending with flour. Mix just until combined.

Divide batter evenly among prepared trays. Tap trays on the counter to release air bubbles. Bake for 18 to 20 minutes, until a wooden pick comes out clean.

Let cool in trays for 10 minutes, then invert onto a wire rack to cool completely, about 1 hour.

When cakes are cool, microwave 1/4 cup milk for 1 minute until hot. Add lavender and let steep for 10 minutes. Strain the milk through a fine mesh strainer, discarding the lavender.

In a medium bowl, combine powdered sugar, salt, and vanilla. Gradually stir in the steeped milk, 1 teaspoon at a time, until you have a smooth, pourable glaze.

Drizzle the cooled cakes with the lavender glaze. Garnish with additional lemon zest and edible flowers, if desired.