Savory Roasted Sweet Potatoes and Cipollini Onions

Last year I shared a recipe for sweet potatoes that is well, sweet. This one is savory. For people who think that they do not like sweet potatoes, they haven't found the right recipe! This recipe has Cipollini onions, during the roasting process they will caramelize. If you live in Phoenix, the farmer's market has sweet potatoes, and they are wonderful. I would get there early this Saturday as it will be a busy one right before the holiday.

4 teaspoons unsalted butter
4 pounds sweet potatoes, peeled and cut into bite sized pieces
about 12 Cipollini Onions peeled
1 teaspoon freshly ground white pepper
1 teaspoon kosher salt
2 teaspoons dried thyme or if you have fresh 6 sprigs with the leaves removed

Heat oven to 375° F. Place the butter on a rimmed baking sheet and put in the oven just long enough to melt the butter. Add the sweet potatoes and onions, stir to get butter on them. Sprinkle with thyme, salt and pepper. Roast, stirring occasionally, until tender, about 45 minutes.