Cook your pasta according to al dente directions.
Dice your onion and garlic. Strain your clams reserving the liquid. Slice your tomatoes in half.
Heat your butter in a large pot. I made this recipe in my trusty dutch oven. It's big enough to handle the job.
Saute until your onions start to brown, 5-10 minutes. Add your garlic and remember it only takes 30-60 seconds for garlic to start to burn. Be prepared.
Add your clam liquid and then cream. Turn heat low enough so it's just under boiling. Stir frequently.
Stir in arrowroot slurry.
Stir in tomatoes and clams and let cook for 2 minutes
Mix in pasta and let cook for 1-2 minutes