Preheat your oven to 350°F (175°C) while you prepare three 8-inch round cake pans. Grease each pan with unsalted butter and dust them with flour.

In a large mixing bowl, combine 1 cup of softened unsalted butter with 2 cups of granulated sugar. Beat until light and fluffy, about 3-5 minutes.

Crack 4 large eggs into the bowl, adding them one at a time and mixing well after each addition.

In a separate bowl, whisk together 2 ½ cups of all-purpose flour, 1 tablespoon of baking powder, and ½ teaspoon of salt.

In another bowl, mix together 1 cup of whole milk, 2 tablespoons of fresh lemon zest, ⅓ cup of freshly squeezed lemon juice, 2 teaspoons of finely ground culinary lavender, and 1 teaspoon of vanilla extract.

Gradually add the dry mixture to the butter-sugar mixture, alternating with the wet mixture, mixing until just combined.

Divide the batter evenly among the prepared cake pans, smoothing the tops with a spatula.

Bake for 25-30 minutes, or until golden brown and a toothpick comes out clean.

Cool the cakes in their pans for about 10 minutes, then turn them out onto wire racks to cool completely.

For the frosting, beat 1 ½ cups of softened unsalted butter until creamy. Gradually add 5 cups of powdered sugar, ¼ cup of heavy cream, 2 teaspoons of lemon extract, 1 teaspoon of vanilla extract, and 1 teaspoon of finely ground culinary lavender. Beat until fluffy.

Assemble the cake by stacking the cooled layers with buttercream in between, then frost the sides and top.

Decorate with additional lemon zest or sprigs of lavender if desired.