Line a full-size sheet pan with parchment paper. Place a wire cooling rack over the sheet pan and spray it with nonstick cooking spray. Place the sheet pan next to a marble surface. Have 3 pairs of latex gloves available.
Place the sugar in a saucepan with about one-quarter of its weight in water or enough to obtain a wet-sand texture. Add the lemon juice to prevent crystallization. Make sure there are no sugar crystals along the inside of the pot and that all the sugar has been hydrated. Begin cooking the sugar over high heat.
Meanwhile, toast the nuts until they have a toasted aroma and a light brown color. If the sugar has not caramelized by this point, keep the nuts hot until it does. If desired, keep them in the oven, but turn it off and open the oven door slightly. If cold nuts are added to the sugar, it will crystallize.
Continue to cook the sugar until it reaches 170°C / 338°F. Turn the heat down to low and stir in the toasted nuts. Make sure all the nuts are coated in sugar, and continue to stir until you start hearing a popping sound, after about 2 minutes, then pour the contents of the pot over the greased wire rack.
Put on the 3 pairs of gloves and spray nonstick cooking spray on them. Working very quickly, separate the nuts from each other and immediately place them on the marble to cool quickly.
Once they have cooled, reserve them in an airtight container at room temperature. Use silica gel packs to absorb any moisture in the container. If properly stored, they can keep for up to 1 week.