Preheat the oven to 400°F and set a rack in the center of the oven.

Bake the onions. Add the onions to a large 13” baking dish, then cut the top off a head of garlic, exposing all the cloves, and nestle into the onions. Drizzle the olive oil, a good sprinkling of salt, and the cayenne onto the onions and the garlic, then toss the onions to coat. Add the beef bone broth to the pan, then distribute the cubed butter on top and cover tightly with foil. Bake for one hour, tossing the onions halfway through, then remove the garlic and continue cooking the onions (covered) for another hour, again stirring halfway through.

Cook the pasta and prep the sauce. When the onions have 15 minutes left, bring a large pot of water to a boil, then add a couple handfuls of kosher salt and cook the pasta till the al dente time on the package. Reserve 1-2 cups of salty, starchy pasta water and drain. While the water is coming to a boil, blend the heavy cream with the cottage cheese and dijon mustard and set aside.

Finish and serve. Take the onions out of the oven and uncover. Squeeze the roasted garlic into a free spot on the pan, mash with a fork and stir everything together. Add the blended cream sauce, gruyere, and fresh oregano into the pan and toss everything together, then add the al dente pasta and a splash of pasta water and toss again until combined, adding more pasta water as needed till you get the consistency you like. Enjoy immediately!