Preheat your oven to 350°F (175°C). Line a 12-cup muffin tin with cupcake liners.
In a medium bowl, whisk together the flour, baking powder, and salt.
In a large bowl, cream together the softened butter and sugar until light and fluffy.
Beat in the eggs one at a time, mixing well after each addition.
Gradually add the dry ingredients to the wet ingredients, alternating with the milk, beginning and ending with the dry ingredients. Mix until just combined.
Stir in the lemon juice, lemon zest, and dried culinary lavender.
Fill each cupcake liner about ¾ full.
Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean.
Let the cupcakes cool in the muffin tin for a few minutes before transferring them to a wire rack to cool completely.
In a large bowl, cream together the softened butter and powdered sugar until light and fluffy.
Add the milk, dried culinary lavender, and vanilla extract and beat until smooth. If desired, add a drop or two of purple food coloring for a lovely hue.
Once the cupcakes are completely cool, frost them with the lavender buttercream frosting.