Bring a large pot of generously salted water to a boil. Cook the wide egg noodles according to the package directions until just tender, then drain well without rinsing.

While the noodles cook, melt the butter in a large skillet or Dutch oven over medium heat. Add the onion and cook for 4–6 minutes, stirring occasionally, until softened and lightly golden.

Add the sliced cabbage, kosher salt, black pepper, and optional garlic powder. Cook for 10–15 minutes, stirring regularly, until tender with some browned edges; add 1–2 tablespoons of water if the pan becomes dry.

Add the drained noodles to the cabbage mixture and toss thoroughly. Continue cooking for 2–3 minutes so the noodles absorb the buttery cabbage and onion flavor.

Stir in the cooked crumbled bacon, if using. Taste the haluski and adjust the salt and pepper before serving.