In a 6-quart Instant Pot, stir together the beans, 2 teaspoons salt, the baking soda and 6 cups water, then distribute in an even layer. Lock the lid in place and move the pressure valve to Sealing. Select Pressure Cook or Manual; make sure the pressure level is set to High. Set the cooking time for 5 minutes. When pressure cooking is complete, quick-release the steam by moving the pressure valve to Venting. Press Cancel, then carefully open the pot. Using potholders, carefully remove the insert from the housing and drain the beans in a colander; return the insert to the housing. Rinse the beans under cool water, set aside. Select More/High Sauté on the Instant Pot. Add the oil and heat until shimmering. Add the onion, garlic, fennel seeds, pepper flakes and 1 teaspoon salt, then cook, stirring occasionally, until the onion begins to soften, about 3 minutes. Add the tomatoes with their juices and cook, stirring occasionally, until the liquid has almost evaporated, 6 to 7 minutes. Add the beans and Parmesan rind (if using), then stir in 3 cups water; distribute in an even layer.