Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper.
In a mixing bowl, whisk together the flour, sugar, baking powder, and salt.
In another bowl, beat the eggs, vanilla extract, and orange zest until combined.
Gradually add the wet ingredients to the dry ingredients, mixing until a dough forms. Stir in the almonds.
Divide the dough in half and shape each half into a log about 12 inches long. Place the logs on the prepared baking sheet and flatten them slightly.
Bake for 25-30 minutes, or until the logs are golden brown. Remove from the oven and let cool for 10 minutes.
Reduce the oven temperature to 275°F (135°C). Using a sharp knife, cut the logs into ½-inch thick slices. Place the slices cut side down on the baking sheet.
Bake for another 10-15 minutes, or until the biscotti are dry and crisp. Let cool completely before serving.