1. Cook the Barilla® pasta for half the time indicated on the package. Drain pasta and drizzle with some olive oil to prevent from sticking. Place pasta flat on sheet trays or hotel pans and cool in a blast chiller. Alternatively, cool it down in a walk-in cooler. Store in zip lock bags or sealed plastic container; refrigerate and use within several hours.
2. To make the pesto: In a food processor, pulse the pinenuts and garlic until chopped. Transfer to a larger container and use an immersion blender to belend in 4 lbs. of the spinach, 4 cups oil, and 6 cups Parmesan until smooth. Season with salt and pepper. Cover and refrigerate until needed.
3. To cook the salmon: Season one side of each fillet liberally with salt and pepper. Sprinkle with 1 tsp. lemon zest and rub with 1 Tbsp. oil. Line sheet pans with foil and layer them with the sliced lemons. Place the salmon on top. Broil until no longer translucent and the salmon is firm when pressed, about 10 minutes. Remove and sprinkle the salmon with 6 oz. lemon juice. When cool, flake the salmon with a fork, discarding the skin. Refrigerate.
4. For each serving, to order: Simmer 1/2 cup cream until reduced by half. Add about 1 cup pesto, 1 cup spinach, 1/2 tsp. horseradish, and 1/4 cup Parmesan. Cook until the cheese melts and the spinach wilts.
5. Reheat 2 cups pasta in simmering water. Drain and plate with the pesto mixture, 6 oz. salmon, and additional Parmesan for garnish.
