Whisk the salt, sugar and lemon zest together. Spread half of the mixture in an even layer along the base of a medium-sized container.
Using the back of a tablespoon, create two indents in the salt/sugar mixture. Place the yolks in the indents and gently cover them with the remaining salt/sugar mixture. Seal the container and place it in the fridge. Leave the eggs to cure for 48 hours.
Once 48 hours have elapsed, preheat the oven to 200°F. Take the yolks out of the salt/sugar mixture and rinse. Set them on a drying rack suspended over a baking tray. Bake for 2 hours or until the yolks reach the texture of hard cheese.
Take the yolks out of the oven and let cool completely before storing.
Scallion Yogurt Rigatoni
Fill a large pot with water and bring to a boil. Add the rigatoni and cook according to the package's directions.
While the pasta is cooking, melt the butter and heat the olive oil in a large, deep skillet over medium heat. Once the butter is foamy and the oil is shimmering, add the scallions and a healthy pinch of salt. Reduce the heat to low and sweat the scallions for 3-5 minutes or until fairly soft. Remove from the heat and stir in the lemon juice.
Transfer the scallions to a food processor. Add the garlic and blitz until smooth. Pour the puree into the skillet and return to low heat.
Add the yogurt, salt and onion powder to the skillet and stir to combine. Gently heat the mixture until bubbles begin to form on the surface. Turn off the heat.
At this point, the pasta should be done. Drain the rigatoni and add it to the skillet. Toss to coat with sauce.
Divide the pasta amongst four bowls. Add a smattering of arugula, a handful of chopped pistachios, and a healthy sprinkling of shredded cured egg yolk. Serve immediately.