Step 1: Cook the Pasta
Bring a large pot of water to a rolling boil. Add the 1 tablespoon of kosher salt. Add the bowtie pasta and cook according to package directions until al dente. Reserve 1 ½ cups of the starchy pasta water before draining. This liquid gold is crucial for adjusting the sauce consistency later. Drain the pasta and set it aside.

Step 2: Brown the Ground Beef
While the pasta cooks, heat a large, deep skillet or Dutch oven over medium-high heat. Add the ground beef and diced onion. Cook, breaking up the meat with a wooden spoon, until the beef is no longer pink and the onions are softened, about 5-7 minutes. In the last minute of cooking, add the minced garlic, dried oregano, and red pepper flakes (if using), cooking until fragrant.

Step 3: Drain and Season
Drain off any excess grease from the beef mixture. Season generously with salt and black pepper. Transfer the beef mixture to a separate bowl and set aside.

Step 4: Create the Roux
In the same skillet, reduce the heat to medium. Melt the 3 tablespoons of butter. Once melted and slightly foaming, sprinkle the 3 tablespoons of flour over the butter. Whisk constantly and cook for 1-2 minutes until the mixture is bubbly and has a light, nutty aroma. This cooks out the raw flour taste.

Step 5: Build the Cream Sauce
Gradually pour in the warm milk and heavy cream, whisking continuously to ensure no lumps form. Bring the mixture to a gentle simmer, continuing to whisk. It will slowly begin to thicken. Allow it to simmer for 3-4 minutes until it coats the back of a spoon.

Step 6: Incorporate the Cheese
Reduce the heat to low. Gradually add the freshly grated Parmesan cheese, one handful at a time, whisking until each addition is fully melted and incorporated before adding the next. This patience ensures a smooth, silky sauce. Stir in the nutmeg and Italian seasoning.

Step 7: Combine and Finalize
Add the cooked, drained beef and onion mixture back into the skillet with the creamy Parmesan sauce. Stir to combine. Add the cooked bowtie pasta and toss everything together until the pasta is evenly coated. If the sauce is too thick, gradually add the reserved pasta water, a ¼ cup at a time, until your desired consistency is reached. The sauce should cling to the pasta beautifully. Stir in the fresh parsley. Taste and adjust seasoning with salt and white pepper. For a final touch of brilliance, add a small squeeze of fresh lemon juice to balance the richness.