First, cream together butter and sugar.
Then, add egg, vanilla extract, and honey, and mix well.
Using either a mortar and pestle or a food processor, grind together the lemon zest and lavender until the aromas of both ingredients are released through the oils. In a food processor, this will take just a moment, but if using a mortar and pestle, it will take a minute or two.
Add the lemon zest/lavender mixture to the bowl with the butter, sugar, egg, vanilla, and honey, and mix until it's evenly distributed throughout.
In a separate bowl, stir together the dry ingredients of flour, baking powder, and salt.
Add dry to wet ingredients and mix.
Form the dough into a ball, wrap in plastic wrap, and place in the refrigerator for about an hour. It will be easier to roll out the dough once it's chilled a bit, plus this chilling helps the cookies keep their shape during baking.
Once the dough has chilled for an hour, preheat oven to 350℉.
On a lightly floured surface, roll out the dough until it's just slightly less than ¼" thick.
Next, cut out the cookies in any shape you'd like and place on a lined baking sheet.
Bake on the center rack of the oven for 10 to 12 minutes. They won't brown like many other cookies and the color actually won't change much, aside from maybe just a little golden hint at the edges.
Let cool and enjoy with a hot cup of tea!