Preheat oven to 425°F.

Coarsely chop Swiss chard, discarding any tough stems. Wash thoroughly and set aside. Scrub potatoes and cut into bite-sized wedges; place in a small saucepan and cover with cold water. Add a pinch of salt, place over medium-high heat and cook until barely tender, about 5 minutes. Meanwhile, Place chicken broth and saffron, if using, in a small saucepan over medium-high heat. Bring to a bare simmer, reduce heat, and keep warm. When potatoes are done, drain and reserve off the heat.

Meanwhile, place olive oil in a large ovenproof pan over medium heat. When hot, add onion and bell pepper and cook, stirring frequently, until softened, 10 to 12 minutes; do not brown. Add garlic and cook an additional 2 minutes. Add cumin and smoked paprika; combine and cook for 2 minutes, stirring often. Add rice and stir to coat with pan juices; cook, stirring often,until rice just begins to turn translucent. Add warm chicken stock, pork or chicken, and salt, black pepper, and cayenne pepper to taste. Bring to a simmer and cook, stirring occasionally, until most of the broth is absorbed, 8 to 10 minutes. Add Swiss chard and stir until wilted; stir in potatoes and beans. Transfer to the oven and bake until rice is al dente, 12 to 15 minutes. Remove from the oven, cover, and allow to rest for 10 minutes.