Preheat your oven to 350°F (175°C). Line two large baking sheets with parchment paper. If your almonds are not pre-toasted, spread them on a baking sheet and toast in the oven for 5-7 minutes until fragrant and lightly golden. Let cool, then roughly chop.

In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, and salt until well combined.

In a separate medium bowl, or the bowl of your electric mixer, beat the room temperature eggs, vanilla extract, almond extract, and lemon zest until thoroughly combined and slightly frothy.

Gradually add the dry ingredient mixture to the wet ingredients, mixing on low speed (or by hand with a sturdy spatula) until just combined and a stiff dough forms. Be careful not to overmix. Fold in the chopped toasted almonds until evenly distributed.

Divide the dough in half. On one of the prepared baking sheets, lightly flour your hands and shape each half into a log, approximately 12-14 inches long and 2 inches wide. Leave ample space between logs as they will spread during baking.

Bake the logs in the preheated oven for 25-30 minutes, or until they are firm to the touch and lightly golden brown.

Remove the baking sheets from the oven and reduce the oven temperature to 300°F (150°C). Let the baked logs cool on the baking sheets for 10-15 minutes. This cooling period is crucial as it makes the logs easier to slice without crumbling.

Carefully transfer one cooled log to a cutting board. Using a sharp serrated knife, slice the logs diagonally into 1/2 to 3/4-inch thick cookies. Repeat with the second log.

Arrange the sliced biscotti cut-side down on the same parchment-lined baking sheets (you may need to use both sheets again). Return to the oven and bake for another 20-25 minutes, flipping the biscotti halfway through, until both sides are golden brown and crisp.

Transfer the baked biscotti to a wire rack to cool completely. They will continue to crisp up as they cool.