Wash your lemons thoroughly under warm water to remove any surface dirt. Using a sharp vegetable peeler, carefully peel the bright yellow rind off the lemons, leaving the thick white pith behind. Use a chef's knife to cut the peels into very fine, thin matchsticks.

Place your thin slivers into a small saucepan and cover them with cold water. Bring to a rolling boil over medium-high heat and let them boil for exactly 5 minutes. Drain the water completely.

Take your peeled lemons and use a knife to cut away and discard all the remaining fluffy white pith. Chop the bare lemon flesh, collecting all the juices in a bowl, and pick out every single seed. Wrap the seeds tightly in a small piece of cheesecloth tied with kitchen twine.

In your heavy-bottomed saucepan, combine the blanched peel slivers, chopped lemon flesh, collected juices, 3 cups (600g) granulated sugar, 1 cup (240ml) water, and the cheesecloth seed bundle. Bring the mixture to a boil over medium heat, stirring gently until the sugar completely dissolves.

Allow the jam to bubble vigorously, stirring occasionally to prevent sticking. Cook until the thermometer reads exactly 220°F (105°C) and the liquid transforms into a vibrant translucent bright yellow lemon jam. Turn off the heat immediately and use tongs to carefully remove and discard the cheesecloth seed bundle.

Toast a thick slice of golden toasted crusty artisan bread until beautifully browned and warm. Smear the bread generously with the jam, top with finely grated fresh yellow lemon zest, and serve alongside fresh yellow lemon wedges.