Preheat the oven to 350* F. Line a 9x13'' glass or ceramic baking dish with parchment paper (don't use metal or it will leave an awful taste!). Butter the dish/parchment paper well, and set aside. Note: I used a 7x10.5'' dish which had a perfect thickness. A 9x9'' will also work, although you will have to bake it for longer.

In a small bowl, whisk together the flour and the salt. Set aside. If your tea has large leaves, you will want to grind it with a mortar and pestle, food processor, spice grinder, etc. If your tea is already finely ground, you can skip this step.

In a medium bowl, cream together the butter and the sugar. Add the chamomile tea. Mix in the flour-salt mixture one cup at a time until a thick dough comes together. Press the dough into the bottom of the prepared pan in an even layer. Use a measuring cup (or something with a flat surface) to press against the dough and even it out. Bake 20-25 minutes until the crust is light brown. Very important: Cool for at least 20 minutes, until it's comfortable to touch and the crust feels firm. If you don't, the custard will slide under the crust.

While the crust is baking, make the filling. In a medium bowl, whisk together the eggs, sugar, flour, lemon juice, lemon zest, and vanilla extract until smooth and lightly foamy. When the crust has cooled, pour the custard mixture over the crust, and bake for 20-25 minutes until the filling is set and doesn't jiggle too much. You do not want the lemon bars to get browned at all, or they will taste eggy!

Cool the lemon bars completely. I let them sit at room temp on the counter and finish cooling in the fridge. Cut the lemon bars into 12 even squares (mine were 2.3 x 3.5''). Dust with powdered sugar and enjoy! You can also store them in an airtight container in the fridge for up to one week.