1. Place tomatoes in the bowl of a food processor and pulse twice to break up tomatoes; set aside.

2. Cook butter and onion in a medium skillet over medium heat until browned. Add carrot and celery; cook for 2 minutes. Add tomatoes, and reduce heat until mixture just barely simmers. Cook, stirring occasionally, for 30 minutes. Season with salt.

3. Add heavy cream and return saucepan to medium-high heat. Cook, stirring, until sauce is heated through, about 1 minute. Use immediately.