2. In a mixing bowl, combine the flour, sugar, baking powder, baking soda, pepper and salt.
3. Finely grate 1 tablespoon of zest from the lemons and set aside. Squeeze 4 tablespoons of juice through a strainer and reserve.
4. In a separate bowl, whisk the eggs, lemon zest and juice together. Add this to the flour mixture along with the pistachios and stir until a stiff dough forms.
5. Scrape the dough onto a lightly sugared work surface and divide it into 4 pieces. Roll each piece with the palms of your hands into a log slightly shorter than the length of your cookie sheet.
6. Place two logs on each cookie sheet, several inches apart (the logs will double in width). Bake for 15 minutes, until the logs feel set or firm to the touch. Set the cookie sheets on racks and let cool. Reset the oven to 300°F.
7. When cool to the touch, place the logs on a cutting board. With a serrated knife, slice them into 1/2-inch diagonal slices.
8. Lay the biscotti out on the prepared cookie sheets in a single layer and bake for an additional 10 to 15 minutes, until they are dry and lightly toasted. Cool completely.
9. Store in an airtight tin or plastic container at room temperature for up to 2 weeks.