Heat the oven to 350° and line a 9-by-13-inch baking pan with parchment paper. In a small saucepan, melt 1⁄2 stick butter over medium heat. Add the chamomile flowers and then remove the pan from the heat and let steep for 30 minutes. Meanwhile, in a medium bowl, whisk the kamut flour with the all-purpose flour and cornstarch.
Rewarm the 1⁄2 stick butter until liquefied and then pour it through a fine sieve set over the bowl of a stand mixer fitted with a paddle; reserve the chamomile flowers. Add the remaining 1 1⁄2 sticks plus 2 tablespoons butter along with the salt and beat on medium-high speed until the consistency of whipped cream, about 2 minutes. Add 1⁄4 cup sugar, the honey, and lemon zest, and beat on medium speed until smooth and just combined. Sift the dry ingredients into the bowl, add the reserved chamomile, and beat on low speed until just combined.
Scrape the dough into the prepared baking pan and press evenly into the bottom. Bake the shortbreads until golden brown, about 25 minutes. Transfer the pan to a rack and, while shortbreads are warm, sprinkle them evenly with the remaining 2 tablespoons sugar. Using a paring knife, score the top of the shortbreads into 2-by-1-inch bars and then let cool completely. Refrigerate the shortbreads in the baking pan for at least 1 hour and then unmold and cut into individual cookies.