Heat canola oil in a 20-qt brazier over medium-low heat. Add the onions and cook, stirring occasionally, until golden brown, about 45 minutes. (Do not skip this step as the almost-melted onions are key to this recipe.)
Meanwhile, wash kale under cold running water. Drain in a colander but do not dry. Remove and discard thick stems. Cut leaves into ½-inch pieces.
Bring water and 3 Tblsp salt to a boil in a large pot. Cook pasta until just tender, about 8 minutes. (Do not overcook.) Drain and rinse with cool water. Return to the pot and toss with olive oil.
Working in batches, add the chopped kale to the onions. Stir and toss the kale until it wilts and shrinks before adding more. Stir in 1½ Tblsp salt. Cook over medium heat, stirring and tossing, until the kale is wilted and tender but still bright green, 5 to 7 minutes. Transfer to a large bowl and let cool.
Preheat convection oven to 350°F or conventional oven to 375°F. Coat two 2-inch full hotel pans with cooking spray.
Add the pasta to the kale mixture and toss to combine. Add Cheddar cheese and continue to toss until the mixture is well combined. Divide between the prepared pans and spread evenly.
Mix breadcrumbs and Parmesan in a small bowl. Sprinkle each pan evenly with half of the mixture.
Bake until brown and the internal temperature reaches 140°F, 20 to 25 minutes. Serve immediately.
