Preheat the oven to 400°F (200°C).
Prepare the pineapple by cutting off the top and bottom, then slicing it into 1-inch thick rings.
Cut the kielbasa into bite-sized pieces, approximately 1-inch thick.
In a small bowl, mix the brown sugar, soy sauce, and Dijon mustard until well combined.
Layer the pineapple slices in a baking dish and place the kielbasa pieces on top.
Drizzle the prepared sauce over the kielbasa pieces, ensuring each bite gets a coating.
Bake in the preheated oven for 25-30 minutes or until the kielbasa is browned and the pineapple is tender.
Remove from the oven, garnish with fresh cilantro, and serve immediately.
