Wash and dry the sweet potatoes. Prick each potato with a fork and place on a parchment-lined baking sheet. Bake until tender, approximately one hour. When a knife inserted meets no resistance, the potatoes are ready. Remove from oven and cool.
Once cool enough to handle, cut off the top quarter of the potatoes with a sharp knife. Scoop out the flesh of the potatoes leaving about ¼ of an inch around the edges to keep the shape of the potato. Also scoop out the top cut piece and set aside.
In a large skillet, heat the olive oil over medium heat. Add the onion and celery and sauté until tender and translucent, about 5 minutes.
Add vinegar and honey and stir to combine.
Add the dried cherries.
Add the kale and sauté until the kale wilts, approximately 2 minutes.
Add the potatoes and stir to combine.
Remove from the heat and add the yogurt. Stir until completely combined and taste for seasoning.
Spoon the filling into each empty potato, mounding the top. There will be extra filling, which can be baked in a separate small dish.
Top with some feta cheese and place back into the oven to warm through and brown the cheese, approximately 5-8 minutes.
The potatoes can be assembled a day before serving. If doing so, cover with plastic wrap and chill after the potatoes are filled. When ready to serve, let warm to room temperature for one hour before baking.