Preheat oven to 450°F (230°C). Place whole red bell peppers on a baking sheet and roast for about 20 minutes, turning every 5 minutes until skin is charred and blistered.
Transfer roasted peppers to a bowl and cover with plastic wrap or lid to steam for 10 minutes. Peel off skins, remove seeds, and roughly chop the peppers.
Bring a large pot of salted water to a boil. Add cheese tortellini and cook 3-5 minutes according to package instructions. Drain and reserve a small cup of pasta water.
In a blender or food processor, combine peeled roasted red peppers and 1 cup heavy cream. Blend until smooth and creamy.
Heat 2 tablespoons olive oil in a large skillet over medium heat. Add minced garlic and sauté for 1-2 minutes until fragrant but not browned.
Pour in the red pepper and cream mixture, stirring to combine. Let sauce simmer gently for 3-5 minutes to thicken slightly.
Lower heat and stir in grated Parmesan cheese gradually, allowing it to melt fully. Season with salt and freshly ground black pepper to taste. Add reserved pasta water if sauce is too thick.
Add cooked tortellini to the skillet and toss gently to coat with sauce. Cook together for another minute to meld flavors.
Serve immediately, garnished with fresh basil leaves.