Preheat your oven to 400 F (200 C). Toss the cubed butternut squash with 1 tablespoon of olive oil, salt, and pepper. Spread on a baking sheet and roast for 25-30 minutes until tender and caramelized.

In a large pot, warm the remaining olive oil over medium heat until it shimmers. Add the chopped onion and sauté, stirring occasionally, until the onion becomes soft and translucent, about 5 minutes. Ensure you stir frequently to avoid any browning or sticking to the pot.

Add the chopped apples to the pot, maintaining medium heat. Cook for an additional 5 minutes, stirring occasionally. Watch for the apples to soften and release a sweet aroma, indicating they are ready. Ensure they do not stick to the pot by stirring gently, preventing any browning or burning.

Add the ground cumin and coriander to the pot, stirring continuously over medium heat for about 1 minute. Watch for the spices to release their aroma, indicating they are toasting properly. This step enhances the soup's aromatic qualities, so ensure the spices do not burn by keeping them moving in the pot.

Add the roasted squash to the pot with the vegetable broth. Heat over medium, stirring occasionally. Once it reaches a gentle simmer, reduce the heat slightly and let it cook for about 10 minutes, allowing the flavors to blend. The squash should become tender and the broth aromatic.

Remove the pot from heat and use an immersion blender to puree the soup until smooth. Alternatively, blend in batches in a countertop blender, ensuring the lid is secure to avoid spills.

If the soup appears too thick, slowly incorporate water, stirring continuously, until it reaches your preferred consistency. Taste the soup, then adjust the seasoning by adding salt and black pepper incrementally, ensuring a balanced flavor profile. Stir well after each addition to evenly distribute the seasoning throughout the soup.

Gently stir in the apple cider vinegar over medium heat, allowing it to blend thoroughly with the soup. This step introduces a gentle acidity that complements the natural sweetness of the butternut squash and apples, creating a balanced flavor profile. Continue stirring for about two minutes until well combined.

Place the pot back on low heat, allowing the soup to warm slowly. Stir occasionally to prevent sticking and ensure even heating. Continue until the soup is thoroughly warmed and steam begins to rise gently from the surface, indicating it has reached an ideal serving temperature.

Ladle the hot soup into bowls, ensuring an even distribution of ingredients. Finish with a sprinkle of freshly ground black pepper for a hint of spice, or drizzle a small amount of olive oil on top to enhance the soup's smooth texture. Serve immediately to enjoy the warmth and aroma.