Heat the olive oil in a large skillet over medium-high heat. Add the bell peppers, scallion whites and celery and cook, stirring, until soft, about 5 minutes. Add the garlic, tomato paste, cayenne and 1/2 teaspoon salt and cook, stirring often, until the tomato paste turns brick red, about 2 minutes. Stir in the quinoa, then add 2 cups water and the beans. Bring to a simmer and cook, stirring often, until most of the water is absorbed and the quinoa is cooked through, about 15 minutes. Add up to 1/4 cup more water if necessary.
Remove the skillet from the heat and stir in the spinach until just wilted. Stir in 1/2 teaspoon salt and half each of the scallion greens and cheese. Divide among bowls and sprinkle with the remaining scallion greens and cheese. Serve with hot sauce.