Ingredients:

• 3 cups (360g) all-purpose flour
• 2 1/2 teaspoons baking powder
• 1/2 teaspoon baking soda
• 1/2 teaspoon kosher salt
• 2 cups (400g) sugar
• 2 tablespoons lemon zest (from about 4 lemons)
• 1 tablespoon dried culinary lavender
• 1/2 cup (113g) unsalted butter, room temperature
• 1/2 cup (120ml) vegetable oil
• 4 large eggs, room temperature
• 1 teaspoon vanilla extract
• 1/3 cup (80ml) fresh lemon juice
• 1 cup whole milk
• 1 1/2 cup (3 sticks) unsalted butter, room temperature
• 6 cups (680g) powdered sugar
• 1/3 cup (80ml) whole milk
• 1 tablespoon lemon extract