INSTANT POT INSTRUCTIONS: Add the butter & saute the onion and celery in your pot for about 5 minutes. Add the tomatoes (no need to drain the canned tomatoes!), pesto, Oregano & sugar. If using fresh tomatoes, add 1 cup water. Place the lid and cook on high pressure for 25 minutes. Natural pressure release, then blend with an immersion blender. Add evaporated milk, stir and then serve!