Steep the saffron: Gently crush the saffron threads over the hot water and let steep for 10 minutes.
Melt the butter in a large skillet over medium heat. Add the olive oil and toast the rice until fragrant, about 5 minutes, stirring frequently.
Add the red bell pepper, garlic, shallot, and crushed red pepper to the toasted rice and saute until ingredients are softened, about 4 minutes.
Add the infused saffron water, tomato sauce, and vegetable broth, stirring to combine. Season with the salt, pepper, and cumin. Bring to a boil and reduce to a simmer. Cover and cook for 20 minutes. The bottom of the rice should be crispy at the end.
Scrape the crispy rice off the bottom of the pan with a wooden spoon. Fluff the rice and season with more salt if desired.