This super simple recipe is adaptable to all types of vegetables - squash, fennel, carrots, rutabaga, etc.
Preheat the oven to 400 degrees. Peel and chop the squash into 1 inch cubes.
In a frying pan or roasting pan that go on the stovetop, add your vegetables and toss with the olive oil, salt and pepper. Place pan in the oven and roast until tender, anywhere from 20 minutes for fennel or summer squash, to 35-40 minutes for harder winter squash.
Remove the pan from the oven and place over medium heat on the stovetop. Stir the vegetables to loosen from the bottom of the pan and pour in the vinegar. Stir to combine and let simmer until reduced, about 3 minutes. Add the butter and stir to combine. Check for seasoning and serve warm.