One Pot Pasta with Sausage, Onions and Apples

Add oil to a large skillet or Dutch oven, heat over medium-high heat. Add sausage and break up into small pieces. Cook until browned and no longer pink inside. Remove to a paper towel covered plate.
In the same skillet turn heat to medium and melt butter. Then add onions and apples and ½ teaspoon salt. Cook stirring occasionally for about 30 minutes until the onions have caramelized and turned brown and the apples are soft but not mushy and the liquid has been absorbed. Add water if needed to prevent the onions from sticking.
Cook the pasta per package direction in salted water until al dente. Drain and reserve a cup of pasta water.
Add garlic and thyme to the onion mixture and cook an additional minute. Add cooked sausage back to the skillet and stir together with the onions and apples. Add the cooked pasta, chicken broth, vinegar, ¼ cup of the reserved pasta water and 1 ½ teaspoons salt. Stir to combine then add cheese and cook until it has melted. Add additional pasta water a little at a time if it is too dry. Sprinkle with additional cheese if desired.