1. 1 pound lasagna noodles
2. 2 tablespoons extra-virgin olive oil, plus more for tossing
3. 1 onion, finely chopped 2 pounds
4. Swiss chard, stems discarded and leaves chopped
5. 2 garlic cloves, minced
6. Kosher salt and freshly ground pepper
7. Three 15-ounce cans pumpkin puree
8. 1/4 cup heavy cream
9. Pinch of freshly grated nutmeg
10. Pinch of cayenne pepper
11. 4 cups fresh ricotta (32 ounces)
12. 2 large eggs, beaten
13. 2 cups freshly grated Parmigiano-Reggiano cheese (about 6 ounces)
14. 2 cups shredded imported Fontina cheese (about 8 ounces)
Preheat the oven to 400°. In a large pot of boiling salted water, cook the lasagna noodles until just starting to soften, about 3 minutes. Drain well and transfer the noodles to a baking sheet. Toss the noodles with olive oil to prevent them from sticking together.
In a large skillet, heat the 2 tablespoons of olive oil. Add the onion and cook over moderately low heat until softened, about 7 minutes. Add the Swiss chard and cook over moderate heat, stirring frequently, until wilted and no more liquid remains, about 8 minutes. Stir in the garlic and cook until fragrant, about 1 minute. Season the chard with salt and pepper. Transfer to a plate and let cool slightly.
In a medium bowl, mix together the pumpkin puree, heavy cream, nutmeg and cayenne. Season with salt and pepper. In another bowl, mix the ricotta with the eggs, 1 1/2 cups of the Parmigiano, 1 cup of the fontina and 1 1/2 teaspoons of salt.
In a well-buttered, 9-by-13-inch ceramic baking dish, spoon 1/2 cup of the pumpkin mixture in an even layer. Arrange 3 or 4 lasagna noodles in the dish, overlapping them slightly. Spread half of the remaining pumpkin mixture over the noodles in an even layer. Top with half of the Swiss chard and another layer of noodles. Cover with half of the ricotta mixture. Repeat the layering with lasagna noodles, pumpkin, Swiss chard, another layer of noodles and finish with the ricotta mixture.
Cover the lasagna with foil and bake for about 40 minutes, until heated through and slightly firm. Remove from the oven and uncover. Preheat the broiler. Sprinkle the remaining 1/2 cup of Parmigiano and 1 cup of fontina on top of the lasagna and broil about 4 inches from the heat until golden brown and crisp on top, about 4 minutes. Let the lasagna rest for 15 minutes, then cut into squares and serve.
MAKE AHEAD The unbaked lasagna can be refrigerated overnight. Let return to room temperature before baking.