Halve the kielbasa lengthwise and then slice it into 1/2-inch pieces. Heat a large deep skillet or dutch oven over medium heat. Add 1/2 tablespoon oil and the kielbasa. Toss to coat and then cook until browned, about 3 minutes per side. Transfer the kielbasa to a plate.

Return the pan to the stove and reduce the heat to medium low. Add the remaining tablespoon of oil and the onion. Cook, stirring occasionally, until the onion has softened. Add the garlic, cabbage, salt, and pepper. Toss well to combine. Cover and cook, stirring every 4-5 minutes until the cabbage is wilted, about 12 minutes.

Stir in the vinegar and return the kielbasa to the pot. Stir and cover for about 3 more minutes, until the cabbage is tender and the kielbasa is hot. Taste and add salt, if needed. Enjoy!