1. Preheat the oven to 350°F and line a 12-cup muffin pan with cupcake liners.

2. In a medium bowl, whisk together the flour, baking powder, and salt.

3. In a large bowl, beat the butter and sugar until pale and fluffy.

4. Add the eggs one at a time, mixing well after each addition.

5. Mix in the lemon zest, lemon juice, and vanilla extract.

6. Stir in the chopped thyme and rosemary.

7. Add the dry ingredients in batches, alternating with the buttermilk, and mix just until combined.

8. Divide the batter evenly among the cupcake liners, filling each about two-thirds full.

9. Bake for 18 to 22 minutes, or until a toothpick inserted in the center comes out clean.

10. Let the cupcakes cool in the pan for 5 minutes, then transfer them to a wire rack to cool completely.

11. For the frosting, beat the butter until creamy.

12. Add the powdered sugar, lemon zest, lemon juice, and enough heavy cream to make a smooth frosting.

13. Mix in the finely minced thyme or rosemary very lightly, if using.

14. Frost the cooled cupcakes and garnish with extra lemon zest or tiny herb leaves if desired.