Preheat oven to 425 degrees F. Prepare water for pasta and bring to a boil. Season ground beef with 1 teaspoon salt and 1/2 teaspoon pepper.: You will notice a warm, dry scent in the oven as it comes up to temperature, and the boiling water will steam and hum on the stove, signaling readiness. Seasoning the ground beef early helps the salt begin to penetrate the meat, improving its internal seasoning as you brown it. A common mistake is under-seasoning at this stage, which can leave the final dish bland, so don't skimp. If your beef seems wet, pat it lightly first so it browns instead of steams.
Heat a large (mine was 12.5 inch) oven-safe skillet over medium heat. Add in olive oil and 1 tablespoon of butter, then toss in onions with 1/4 teaspoon salt. Stir and cook for 3-4 minutes, until soft. Add in garlic and cook for another minute, then add in ground beef, baking it apart with a spatula or wooden spoon. Cook until just browned, about 5-6 minutes, stirring occasionally. If there is excess liquid in the pan, feel free to drain a bit.: As the fat warms you will hear a gentle sizzle when the onion hits the pan and smell a sweet, toasty aroma as the edges soften. The butter melts and creates a glossy coating that helps the onion sweats rather than browns too quickly. This step builds a savory base, and rushing it can produce raw, sharp onion notes. Stir every minute or so to ensure even softening and avoid scorching.
At this point your water should be boiling, so make sure to toss the broken noodles in and cook them for about 5 minutes. Remove with a slotted spoon or drain and set aside for a few minutes.: The garlic will offer an immediate fragrant lift, and browning the beef will create appetizing brown bits on the skillet surface, full of flavor. You want the beef to be browned but not dry, so listen for a satisfied sizzle and look for even golden coloration. A frequent error is overcrowding the pan, which causes steaming instead of browning. If that happens, brown in batches or drain excess moisture to achieve better crust and deeper flavor.
Once beef is browned, add in tomatoes with remaining butter and the 3 tablespoons of fresh basil, tossing well to coat. Add in broken noodles, using the spatula or spoon to fold the beef and sauce over the noodles. Once noodles are evenly distributed and mostly under the sauce, add sliced mozzarella on top and scoops of ricotta. Bake for 10 minutes, then immediately remove and add torn basil on top. Serve!: The boiling water should be lively, and the noodles will bob and slide as they soften, releasing a faint wheaty steam. Removing them slightly al dente is important since they will finish in the oven, absorbing sauce without turning to mush. A common slip is overcooking the pasta here, which leads to a gummy final texture. Reserve a little pasta water if you like, as the starchy water can help the sauce cling to the noodles.
Once beef is browned, add in tomatoes with remaining butter and the 3 tablespoons of fresh basil, tossing well to coat.: When the crushed tomatoes meet the browned beef, you will hear a softer simmer and smell a rich tomato aroma start to develop. The remaining butter enriches the sauce, smoothing acidity and adding body, while the chopped basil infuses herbal fragrance. Stir until the mixture looks cohesive and glossy. Avoid boiling aggressively, which can dry the sauce; instead aim for a gentle simmer so flavors meld without losing moisture.
Add in broken noodles, using the spatula or spoon to fold the beef and sauce over the noodles.: As you fold, watch the noodles tuck under the sauce and soak up some of the liquid, becoming coated rather than sitting dry. The sound will be a soft, satisfying stir, and visually you should see noodles surrounded by a ribbon of sauce. The reason this folding matters is it ensures even saucing so each bite has balance. A mistake is dumping the noodles on top and not mixing, which creates dry pockets and uneven cooking.
Once noodles are evenly distributed and mostly under the sauce, add sliced mozzarella on top and scoops of ricotta.: Placing slices of mozzarella and dollops of ricotta gives the skillet layers of melty cream that will brown slightly and bubble in the oven. You will smell a rich, dairy sweetness as the cheese heats, and the visual cue is the cheese turning glossy and spreadable. Make sure the cheese pieces are evenly spaced so melting looks and tastes uniform. Avoid piling cheese only in the center which can leave the edges undercheesed.
Bake for 10 minutes, then immediately remove and add torn basil on top. Serve!: In the oven the cheese will bubble and the sauce will quiet into a gentle simmer, producing a toasty, nearly caramelized aroma from the top layer. Removing the skillet immediately prevents the cheese from overbrowning, and adding the torn basil releases a bright, fresh perfume that contrasts the warm, rich notes. A typical misstep is leaving it in too long which can dry the noodles and toughen the cheese; watch the color and remove as soon as it is melted and bubbling.