Preheat your oven to 300°F (150°C).

Rinse the beef spareribs under cold water and pat them dry. Season with salt and pepper to taste.

In a large bowl, combine the soy sauce, apple cider vinegar, brown sugar, minced garlic, chopped onion, and bell pepper. Mix well to create a flavorful marinade.

Add the spareribs to the bowl and ensure they are well-coated in the marinade. For deeper flavor, let them marinate for at least 30 minutes, preferably longer.

Place the marinated ribs in a baking dish and pour the remaining marinade over the top. Cover the dish tightly with aluminum foil.

Bake in the preheated oven for 2.5 to 3 hours until the ribs are tender and fall off the bone.

While the ribs bake, prepare the sauce. In a small saucepan, combine the pineapple chunks (with juice), cornstarch, and water. Cook over medium heat, stirring constantly until the sauce thickens.

Once the ribs are done baking, remove them from the oven. Brush the thickened sauce generously over the ribs before serving.

Garnish with sesame seeds and sliced green onions if desired. Serve warm and enjoy!