In a 5- to 6-quart pan over high heat, bring about 4 quarts water to a boil. Add penne and cook, stirring occasionally, until tender to bite, 10 to 12 minutes. Drain.
Pour oil into the same pan over medium-high heat. Add sausage and garlic and stir, breaking apart with spoon, until sausage is crumbled and brown, about 10 minutes.
Add chard and stir until wilted, about 5 minutes. Stir in tomatoes with juice, salt, pepper, and cooked pasta. Pour mixture into a 2- to 2 1/2-quart baking dish. Sprinkle mozzarella and parmesan cheeses over the top.
Bake in a 350° oven until cheese is browned and bubbling, 25 to 30 minutes.
This was such a great dish. I wanted to find a way to use the Rainbow Swiss chard that came with my CSA order and came across this recipe using the pantry list search (such a cool tool!). I used fresh chicken sausage and whole wheat rigatoni since that was what I had on hand. My husband and I loved it and the spice of the sausage really offered a nice punch of flavor. I took the suggestion of other reviewers and layered the cheese with the pasta mixture.