Cut the tops off the bell peppers and reserve. Carefully scoop out the seeds and ribs of the bell peppers. Bring a large pot of water to a boil. Add the bell peppers and their tops and boil them for 1 to 2 minutes, or until just softened. Remove the peppers and tops with a slotted spoon and transfer them to a bowl of ice water. Remove the peppers and tops from the ice water and let them dry. With a paring knife, cut out 2 triangles for the eyes and a jagged mouth on each pepper. Set aside.

In a large skillet, heat oil over medium-high heat until hot. Add onion, garlic, salt and black pepper and sauté for 4 to 5 minutes, or until onion is softened. Add tomatoes and bring to a boil. Reduce heat and simmer, stirring occasionally, until sauce thickens, about 15 minutes. Add parsley and simmer another 5 minutes, stirring occasionally.

Meanwhile, cook pasta in a large pot of boiling, salted water until just tender. In a colander, drain pasta and return pasta to pot. Add 1/4 cup tomato sauce to pasta and toss to coat. Transfer pasta to bell peppers, with some pasta sticking out of the “head.” Top with some of the remaining sauce, cheese and additional parsley, if desired. Top with the bell pepper top.