In a sauce pan over medium/high heat, melt butter. Add Celery and Onion. Saute' until tender. Set aside.
In an Instant Pot or Pressure Cooker put Italian Stewed Tomatoes, Pesto Sauce, Sugar, Salt, and Celery/Onion mixture. Add 1/2 cup of water or chicken broth. This is to add enough extra liquid so your ingredients don't burn in your Instant Pot. If cooking in a Crock Pot, do not add extra water. Give a quick stir.
Secure the lid. Check to make sure the pressure value is closed. Set Instant Pot to Manual and cook for 5 minutes. It will take a few minutes for the pressure cooker to heat up and seal. Then it will cook for 5 minutes. Do a quick release to release pressure.
Use an Immersion Blender to blend soup to a smooth consistency. Mine is never smooth because my pesto sauce is still a little chunky which is like. Just blend up as much as you like. If you do not have an immersion blender, you can remove soup and put it in a blender a little at a time. It's super simple and no big deal. Either way works just fine.
Add whipping cream and blend or stir to combine. Serve hot with fresh Parmesan. Oh so good!
In a Food Processor, place Basil, Almonds, Fresh Parmesan, Garlic, and Olive Oil. Blend to combine to desire smoothness. Set aside. (Pesto can be used in a variety of recipes. Added to Alfredo sauce to make a creamy Alfredo too)