This warm, hearty meal comes together on a single sheet pan. Sauerkraut mellows as it bakes, adding just enough tang to balance the smoky sausage and sweet apples.
1 (16-oz.) package cubed butternut squash
1 (14-oz.) package kielbasa, cut into 1/2" slices
2 Tbsp. olive oil, divided
1 cup refrigerated sauerkraut, drained
2 tsp. apple cider vinegar
2 tsp. stone-ground mustard
1 (5-oz.) package baby arugula
1 Fuji apple, cored and thinly sliced
1/2 cup thinly sliced red onion