Slice the kielbasa into 1/2 inch round rounds. Set aside.
Remove the rosemary leaves from the stems and roughly chop. Set aside.
Preheat a large skillet on medium heat. Once skillet is hot, sear the kielbasa pieces for 2-4 minutes, until brown on both sides. Remove from skillet and set aside.
Set the skillet back on the heat with the butter and onions. Sear for 2 minutes to soften, then add the apples and rosemary. Allow apples and onions to cook until soft and brown, but not mushy. Stir gently trying to avoid smashing the apples, about 5-7 minutes. Salt and pepper liberally.
Add the sausage back to the skillet, along with the apple butter, vinegar and 1/2 cup water. Simmer and stir to thicken the sauce for 2-3 minutes.
Salt and pepper as needed. Serve warm.