In a large pot of boiling salted water, cook pasta according to package instructions until al dente; drain well.
Heat 1 tablespoon olive oil in a large cast iron skillet over medium high heat. Working in batches, add zucchini and squash, and cook, stirring occasionally, until golden, about 3-4 minutes; set aside.
Add remaining 1 tablespoon olive oil to the skillet. Stir in sausage, bell pepper and onion until golden, about 4-5 minutes. Stir in garlic and Italian seasoning until fragrant, about 1 minute.
Stir in diced tomatoes. Reduce heat and simmer until slightly thickened, about 7-10 minutes; season with salt and pepper, to taste.
Stir in pasta, zucchini, squash and basil until well combined; sprinkle with cheese.
Place into oven and bake until bubbly and golden brown, about 15 minutes.
Serve immediately.
Notes
Slightly undercook the pasta. This is the secret to avoid mushy, limp noodles. As a general rule, cook the pasta 1-2 minutes less than the package instructions for al dente.
Use a cast iron skillet.Cast iron skillets are oven-safe and have excellent heat retention, allowing for a seamless transition from the stovetop to the oven.
Sauté the vegetables first. Never add raw vegetables directly to the pasta bake. Always pre-cook the vegetables first before assembling the dish for maximum flavor.
Freshly grated cheese goes a long way. Avoid pre-shredded cheese as they contain anti-caking agents that hinder their ability to melt properly.
Broil for 1-2 minutes (optional). Switch the oven to broil for 1-2 minutes to achieve that perfect golden-brown crust on top.
Let it stand for 10 minutes. Allowing the pasta bake to rest for at least 10 minutes will ensure that the pasta mixture will hold up its shape upon serving.
Freeze before baking. This will preserve the texture, preventing the noodles from becoming mushy and the sauce from breaking. This also allows everything to cook together perfectly during the final bake.