Heat your oven to 375F. Line two baking sheets with parchment and set aside.
In a large mixing bowl, cream together the butter and sugar, until pale and fluffy, using an electric mixer.
Add in the egg and lemon zest and blend again until fully incorporated.
Sift the flour and baking powder together and add to the butter mix.
Finally add the flower petals and herbs. Stir with a wooden spoon until combined. Doing the final bit of stirring with your hands is helpful to bring it all together. The dough will seem a bit dry. That's okay.
Place all your dough onto a large piece of plastic wrap and roll it into a log. About 2" in diameter. Make sure it's tightly wrapped in the plastic wrap, then place in the fridge to chill for 30 minutes. (The dough can also be frozen like this.)
After the dough is nice and cold, and firm to the touch, remove from the fridge. Slice the log into 30 pieces about 1/2" thick and arrange them on your baking sheets.
Bake for about 8-10 minutes. Or until the tops have puffed slightly and the edges are beginning to turn golden. Cool on a wire rack.
Store in an air tight container. At room temp the cookies will last for about 2 weeks if sealed tightly. In the fridge they will last upwards of 3 weeks. The cookies can also be frozen.