Place an oven rack in the center of the oven. Preheat the oven to 375 degrees F. Spray a grill pan with vegetable oil cooking spray.
In a Dutch oven, heat the oil over medium-high heat. Add the fennel, onion, 1 teaspoon of the salt and the red pepper flakes. Cook, stirring constantly, until the vegetables are soft, about 5 minutes. Add the tomatoes (plus juices), beans, kale and broth. Bring the mixture to a boil. Cover the pan with a tight fitting lid and transfer to the oven. Cook until the vegetables are tender and the kale has wilted, 25 to 30 minutes.
While the stew is cooking, place a grill pan over medium-high heat or preheat a gas or charcoal grill. Add the sausages and grill, turning occasionally, until cooked through, about 20 minutes. Cool and cut into 1/2-inch-thick slices.
Remove the pan from the oven and add the cooked sausage slices. Season with the remaining 1/2 teaspoon of salt. Spoon the stew into bowls and serve.