1In a large pot of boiling, salted water, cook the pasta to al dente according to package directions. Drain and set aside.
2In a large, deep frying pan over medium-high heat, cook the sausage until browned. Transfer to a bowl, discarding any fat.
3Remove the ribs from the chard. Cut off and discard the bottom inch of the ribs, then finely chop the ribs. Roughly chop the leaves.
4In the frying pan, warm a glug of olive oil. Add the chard ribs and a sprinkle of salt and cook until nearly tender, about 5 minutes. Add the chard leaves and cook for 2 minutes, then add the cherry tomatoes. Add the lemon zest and juice and season with salt and pepper. Add the butter and stir until it melts and forms a velvety sauce.
5Add the pasta to the pan and stir and toss to coat the pasta with the sauce and warm it through, about 3 minutes. Serve with the Parmesan sprinkled over the top.