Roast the bell pepper over a gas flame, turning until charred all over (or place under a broiler until charred). Carefully wrap the pepper in paper towels and place it in a plastic bag. Let it stand until cool. Rub the charred skin from the pepper with paper towels. Core the pepper; roughly chop.

Place the pepper, garlic, and cream in the container of a food processor or blender. Process until smooth.

Melt the butter in a medium saucepan over medium-low heat. Whisk in the tomato paste and the pepper-garlic purée. Add the sage, paprika, and salt to taste. Cook, without boiling, until hot.

Stir in the cheese and hot cooked pasta. Serve immediately.