Heat the butter and olive oil in a large sauté pan over medium heat. Add the sliced onions and a generous pinch of salt. Cook, stirring occasionally, until the onions become deeply golden and caramelized, 25-30 minutes. If the pan begins to dry out, reduce the heat slightly or add a splash of water. Season with salt once onions are caramelized.

Stir in the minced garlic and cook for 1–2 minutes, until fragrant. Add the balsamic vinegar and cook for another minute. Pour in the cooking cream and bring to a gentle simmer. Reduce the heat to low and stir in the parmesan cheese. Season with salt, pepper, and the juice of half a lemon. Let the sauce thicken slightly while you cook the pasta.

Bring a large pot of salted water to a boil. Cook your pasta of choice according to package instructions until al dente. Reserve ½ cup of the pasta water, then drain.

Add the cooked pasta directly into the onion cream sauce, tossing until fully coated. If needed, add a splash of the reserved pasta water to loosen the sauce and help it cling to the noodles.

Divide the pasta among bowls and garnish with chopped parsley, an extra squeeze of lemon juice, freshly grated parmesan, and a sprinkle of salt and pepper to taste. Serve and enjoy!