Preheat the oven to 350 degrees F. Butter a 3-quart baking dish. Melt 6 tablespoons butter in a large skillet over medium heat.
Add the onion and 1/4 teaspoon sugar and cook until soft and golden brown, 8 to 10 minutes.
Transfer to a large bowl, reserving the skillet.
Meanwhile, bring a large pot of salted water to a boil; add the noodles and cook until al dente, about 6 minutes.
Drain the noodles and add to the bowl with the onion mixture; season with salt and pepper.
Pulse the eggs, cottage cheese, sour cream, milk, cinnamon, orange zest, the remaining 1 tablespoon sugar and 1 teaspoon salt in a food processor until smooth.
Add to the noodles and toss, then transfer the mixture to the prepared dish. Melt the remaining 2 tablespoons butter in the skillet over medium heat, add the cornflakes and toss.
Sprinkle over the pasta and bake until just set, 35 to 40 minutes.