Preheat oven to 300 degrees. Line a baking sheet with a silicone baking mat or parchment paper.

In a mixing bowl, whisk together the gluten free flour, salt and baking powder.

In a mixer fitted with a whisk attachment or with a handheld at medium speed, beat the olive oil with the sugar, vanilla, lemon zest and eggs until well combined. Turn mixer to low, gradually add the flour mixture. Add the pistachios and stir by hand to combine. Place dough on prepared baking sheet and form into a log which is roughly 12 inches long by 4 inches wide and ½ inch high. If dough is too sticky, wet your hands with water. Bake for 50 minutes or until golden brown. Remove from oven, increase heat to 350 degrees and cover the biscotti with two tea towels and let cool for 10 minutes.

Remove the log from the baking sheet and place on a cutting board. Using a thin, sharp knife, cut the biscotti on a diagonal into ¾ inch slices and place the slices back on the baking sheet. Bake for 10 minutes or until the biscotti are golden brown.

Store in an airtight container, especially important if the air is humid.