Step 1

Line a 9-inch round cake pan with cooking spray and parchment paper. Set aside.

Step 2

Make the crumb topping: In the bowl of a stand mixer fitted with a paddle attachment, beat 1 ½ cups flour, brown sugar, cinnamon, ¼ teaspoon salt, and ¾ cup butter until mixture resembles wet sand.

Step 3

Transfer to a small bowl and set aside.

Step 4

Preheat oven to 350 F.

Step 5

In the same stand mixer bowl, beat remaining ½ cup butter with granulated sugar until smooth.

Step 6

Add eggs one at a time, mixing until each is combined with the creamed butter and sugar. , Scrape down the bowl with a rubber spatula after each addition if needed.

Step 7

Add 1 ½ teaspoons vanilla extract, ½ cup sour cream, and lemon zest. Beat to combine.

Step 8

Add 2 cups flour, baking powder, baking soda, and remaining ¾ teaspoon salt. Beat just until no flour remains visible.

Step 9

Add remaining ½ cup sour cream. Beat until batter is smooth.

Step 10

In a small bowl, toss blueberries with remaining 1 tablespoon flour to coat.

Step 11

Pour cake batter into prepared pan and spread evenly.

Step 12

Top with blueberries and 1 teaspoon lavender flowers.

Step 13

Add crumb topping in an even layer.

Step 14

Bake for 60 to 75 minutes or until a wooden pick inserted in the center comes out clean.

Step 15

Transfer to a wire rack and cool for at least 1 hour.

Step 16

Make the glaze: In a small bowl, stir to combine confectioners' sugar, remaining ½ teaspoon vanilla extract, ½ teaspoon lavender flowers, and 1 tablespoon lemon juice.

Step 17

If the glaze is too stiff, stir in a splash of water or milk. Repeat if necessary until you get a pourable consistency. Add food coloring if desired.

Step 18

Drizzle glaze over cake and sprinkle with remaining ½ teaspoon lavender and additional confectioners' sugar, if desired.

Step 19

Serve warm or at room temperature.