Set the Instant Pot to 'Sauté' mode and adjust the setting to ’Normal'. When the display reads 'Hot', add butter or oil.
Add cashews, onions, black peppercorns, and garlic. Sauté till the onions are soft and translucent.
Add chopped tomatoes and mix well.
Add water, along with salt, and mix well.
Cover the lid, move the vent to "sealing" and pressure cook on high for 10 minutes. When the cooking cycle is complete, do a quick release i.e move the steam valve to "venting".
Open the lid and add basil leaves. Use an immersion blender to puree the soup. If using a blender to puree, wait at least 10-15 minutes for the soup to cool down.
Do a taste test and add salt and pepper if needed. If the soup is too tart, you can add a teaspoon of sugar (or more) to tone down the sourness.
Serve immediately with bread, oyster crackers, or enjoy as-is.
Notes
Notes/ TipsThis soup can be stored in the refrigerator for 4-5 days and up to a month in the freezer. Ingredient swaps
Butter is a great flavor enhancer in this dish. For a vegan version, substitute olive oil or avocado oil.
You can replace water with vegetable broth to make it more flavorful.