Preheat the oven to 375 degrees F. Line a baking sheet with parchment. Rub the outside and inside of squash and 2 or 3 whole garlic cloves with olive oil, and sprinkle inside of squash with salt. Mince remaining 3 garlic cloves and set aside.
Put a clove of garlic in each half and place squash cut side down on the parchment lined baking sheet, with the clove of garlic in the well of each squash.
Roast for 35-40 minutes, until squash is very tender and fork slides through the flesh without any resistance. Let cool a bit before scooping out flesh from the skin. Compost the skin.
Meanwhile, heat 1 tablespoon olive oil in a saucepan over medium heat. Add onion and sprinkle with 1/4 teaspoon salt, and saute 7-8 minutes, until translucent. Add minced garlic and smoked paprika, stirring to coat the onion. Cook for 1 minute, then add roasted red peppers, 3 1/2 cups stock, and roasted squash. Simmer for 15 minutes.
Remove from heat and stir in apple cider vinegar. Blend soup in a blender until completely smooth. If you'd like it thinner, add the remaining 1/2 cup stock. Taste and add 1/4 teaspoon additional salt at a time if needed, so you're able to taste the smokiness and deliciousness of a well seasoned soup.