Preheat your oven to 375°F (190°C) and grease a baking sheet or line with parchment paper.
In a large bowl, whisk together the brown sugar, soy sauce, apple cider vinegar, garlic powder, and ground ginger until smooth and sugar dissolves completely, about 30 seconds.
Pat pineapple chunks dry with paper towels. Add the kielbasa pieces and pineapple to the bowl with the glaze. Toss until everything is evenly coated with the mixture.
Spread the glazed kielbasa and pineapple in a single layer on the prepared baking sheet, leaving space between pieces for proper caramelization.
Bake for 20-25 minutes, stirring once at the 10-12 minute mark, until the kielbasa has golden-brown, slightly crispy edges and the glaze is bubbly and caramelized. Watch carefully in the last 5 minutes to prevent burning.
Remove from oven and let cool for 2-3 minutes to allow glaze to thicken. If desired, garnish with sliced green onions and sesame seeds before serving warm.
Notes
Use pineapple packed in juice rather than syrup for better flavor balance. Drain well and pat dry to help the glaze caramelize properly.
Dark brown sugar adds deeper molasses flavor, but light brown sugar works great too.
These taste even better the next day after flavors meld. Make ahead and reheat at 350°F for 8-10 minutes.
For slow cooker method: combine all ingredients and cook on high for 2-3 hours or low for 4-5 hours.