Bring a large pot of salted water to a boil. Meanwhile, in a large skillet, cook the bacon over medium heat until golden, about 8 minutes. Push the bacon to the side of the pan and add the onion; season with salt and pepper. Cook until the onion is softened, 6 to 8 minutes. Add the diced tomatoes, season with salt and pepper and simmer, stirring occasionally, until thickened, 15 to 18 minutes. Stir in the parsley.

Meanwhile, add the green beans to the boiling water and cook until crisp-tender, about 3 minutes. Using a slotted spoon, transfer the beans to a colander; season with salt and pepper and cover to keep warm.

Return the water to a boil, add the noodles and cook until tender, about 9 minutes. Drain, reserving 1 cup of the cooking water. Toss the noodles with the sauce, adding the pasta water if needed to thin the sauce; season. Divide among 4 plates; serve with the green beans.