Grilled Keilbasa with Sauerkraut and Onions

This was such a nice dinner.  I love how the sweetness of the sauce went perfect with the tanginess of the sauerkraut.  Great dinner.  Enjoy!
For main dish:
-1 1/2 lbs smoked Polska kielbasa
-2 Tbs butter
-3 Tbs sugar
-1 medium onion, sliced
-2 (14.5 oz each) cans sauerkraut, drained (not rinsed)
For the sauce:
-1/4 cup yellow mustard
-1/4 cup honey
-1/4 cup Dijon mustard
-1/2 tsp cayenne
-1 Tbs prepared horseradish
-pinch of salt
-pinch black pepper
Preheat grill.  Preheat oven to 400 F.
Cut kielbasa into 3 inch lengths and butterfly lengthwise.  Place on hot grill and cook until each side is nicely charred.  Remove from grill into baking dish.  Place in preheated oven and bake for about 6 minutes.
Meanwhile, in a large skillet add butter and sugar.  Cook until butter is melted and sugar is golden brown.  Add onions and cook until caramelized, about 5 minutes.  Stir in sauerkraut and cook for about 10 minutes.
Remove kielbasa from oven and cut into 1 inch chunks.  Stir into sauerkraut mixture.  Cook for about 1 minute. 
Mix together all sauce ingredients.  Blend well. 
Serve the sauerkraut mixture with a little of the dipping sauce.  Enjoy!
Slightly adapted from an Aaron McCargo Jr. recipe.