Bring a large pot of salted water to a boil. Combine the olive oil, spring onion whites and a pinch of salt in a large skillet over medium heat. Cook, stirring, until soft and just golden, about 5 minutes. Add the tomatoes, then fill the tomato can with water and add to the skillet; season with pepper. Increase the heat to high and cook, stirring, until the tomatoes burst and the sauce thickens, 13 to 15 minutes. Remove from the heat and swirl in the butter until incorporated.
Meanwhile, cook the ravioli in the boiling water as the label directs. Reserve about 1/2 cup cooking water, then drain. Add the ravioli and half the spring onion greens to the tomato sauce. Cook over medium-high heat, tossing gently, until well coated. Stir in enough of the reserved cooking water to loosen the sauce. Divide the ravioli among bowls; top with the remaining spring onion greens and season with salt and pepper.