1) Cook macaroni according to package directions.
2) Meanwhile, chop and saute onion until tender. Shred cheddar cheese. Preheat oven to 175°C (350°F).
3) In a blender, combine the sauce ingredients; process until smooth.
4) In a large bowl, mix everything together. Pour into a 1-1/2-qt. baking dish coated with cooking spray. Bake, uncovered, for 20-25 minutes or until lightly browned.
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