In a small bowl or jar, combine ¼ cup of olive oil, 2 tablespoons of red wine vinegar, 1 tablespoon of mustard, ¼ teaspoon of garlic powder, and salt and pepper to taste. Whisk or shake well until the mixture is emulsified and combined.

Slice the kielbasa into medallions about ½ inch thick. Heat 1 tablespoon of olive oil in a large skillet over medium heat. Add the kielbasa slices, and cook for 5-7 minutes, stirring occasionally until they are golden brown and slightly crispy on the edges.

Add the diced yellow onion to the skillet with the browned kielbasa. Stir well to combine and sauté for about 5 minutes, or until the onions become translucent and soft.

Chop half a head of cabbage into bite-sized pieces and add it to the skillet. Season with salt and pepper. Stir to mix everything well, then sauté for about 8-10 minutes.

Once the cabbage is tender and well mixed with the kielbasa and onions, drizzle half of the mustard vinaigrette over the skillet. Stir to coat all the ingredients in the tangy sauce.

For a fresh finishing touch, consider garnishing your Kielbasa and Cabbage Skillet with chopped fresh herbs like parsley or sliced green onions before serving.