1 Cook the bacon and onions in the pressure cooker: Select the “Sauté” setting and add the bacon to the pressure cooker. (If you are using a stovetop pressure cooker, use medium heat.)
Let the bacon cook until it has rendered some fat and begun to brown a bit, about 7 minutes. Add the onions and sauté until softened and translucent, about 3 more minutes.
2 Stir in the rest of the ingredients and pressure cook: Add the green beans, diced tomatoes and their liquid, water, salt, pepper, cayenne, and thyme. Give everything a good stir so all of the green beans are coated with some of the cooking liquid.
Secure the lid on the pressure cooker. Make sure that the pressure regulator is set to the “Sealing” position. Cancel the “Sauté” program on the pressure cooker, then select the “Manual” or “Pressure Cook” setting. Set the cooking time to 7 minutes at high pressure. (For stovetop pressure cookers, cook for 6 minutes at high pressure.)
It will take about 10 minutes for your pressure cooker to come up to pressure, and then the 7 minutes of actual cooking will begin.
3 Release the pressure: Perform a quick pressure release by immediately moving the vent from “Sealing” to “Venting” (be careful of the steam!). The pot will take a couple minutes to fully release the pressure.
4 Serve the green beans: Use a slotted spoon to gently transfer the green beans to a serving dish. Scoop up the tomatoes, bacon, and onions, and spoon them over the top of the beans. Serve hot.