To make the lasagna noodles, pile two cups of all-purpose flour onto a hard surface such as the counter. Make a well in the center of the flour and crack in three eggs, plus one egg yolk. Sprinkle the eggs with salt. Whisk the eggs together, gradually incorporating the flour. Then, use your hands to knead the dough for about five minutes. Shape into a disk and wrap the dough in plastic wrap. Set on the counter for 30 minutes to rest.
While the dough rests, marinate the ground pork. Let marinate in the refrigerator for 30 minutes.
When the dough is ready, divide into quarters and working in batches roll the dough out until thin, about 1/16ths of an inch thick. I use my KitchenAid to roll out the dough to a #6. If using a rolling pin (which works just as well), roll the dough out to as thin as you can get it. Cover the sheets of pasta and set aside.
Fry the sausage until cooked through, then set aside to drain on a few paper towels.
Make the ricotta mixture and set aside.
Next, thinly slice two lemons (the one you zested for the ricotta mixture) plus one more. Re move the seeds from the lemon slices and add to a large steep-sided skillet. Fill the pan with just enough water to cover the lemons. Bring the water to a boil and cook the lemons for 5 minutes until soft. Remove the lemons from the water and set aside.
It's now to time assemble the lasagna. Preheat the oven to 375°F and grab and 8x8 inch square pan.
Add ½ cup of cooked sausage and a heaping ⅓ cup of ricotta cheese to the bottom of the pan. Cover with the pasta noodles, cutting them to size so that they do not overlap, but cover the underneath layer. Top the noodles with a heaping ⅓ cup of ricotta cheese, ⅓ cup of shredded parmesan and ½ cup of sausage. Layer on half the lemon slices, then top the lemons slices with another layer of pasta. Repeat with another layer of ricotta cheese, parmesan cheese and sausage, but omit the lemon slices. Cover with noodles and repeat again. Top this final layer with one last layer of pasta, arrange the last of the lemon slices on top and sprinkle with the remaining parmesan cheese.
Bake the lasagna for 40-45 minutes or until golden on top and bubbly. Let rest for 5-10 minutes before serving. Enjoy!