Start by bringing a large pot of salted water to a boil and cook the spaghetti according to package instructions until al dente, usually about 8-10 minutes. Once cooked, promptly drain the pasta in a colander and give it a quick rinse under cold water to stop further cooking. Set aside to cool slightly while you prepare the sauce.

In a large mixing bowl, combine the drained spaghetti with 3 cups of marinara sauce and half of the shredded mozzarella cheese for a cheesy, flavorful blend. If you’re opting for a heartier version, add in the seasoned ground beef or sausage. Mix everything together until the pasta is well-coated and you can see the vibrant red sauce throughout the mixture.

Grease a bundt pan well to ensure easy release later, or you can freestyle by molding the pasta into a brain shape directly on a baking sheet. Use your hands to press and shape the spaghetti mixture tightly, creating folds and ridges that mimic a brain's texture for that eye-catching effect.

Carefully arrange the spaghetti strands to enhance the brain-like appearance—think of how folds might look. Use additional marinara sauce to create 'bloody' detail over the top, ensuring it seeps into the grooves.

Sprinkle the remaining shredded mozzarella cheese generously over the pasta, covering every visible area. This layer will melt beautifully and create an appealing, bubbly crust as it bakes.

Preheat your oven to 350°F (175°C). Once it’s ready, place your assembled Spaghetti Brain Bake in the oven. Bake for 25-30 minutes until the cheese is golden brown and bubbly.

After baking, carefully remove your Spaghetti Brain Bake from the oven. Let it cool for about 10 minutes to allow the cheese to set slightly, making it easier to slice.