4. Cook Sofrito
Reduce the heat to medium and add another tablespoon of oil to the pot. Add the onions and cook until softened, about 5 minutes. Add the garlic, paprika, and saffron and continue to cook, stirring constantly, until the garlic starts to brown, about 20 seconds. Add the tomato and cook until its liquid has evaporated and the mixture becomes jammy, about 5 minutes.
Add the stock, rice, and 1 ½ teaspoon salt and bring to a simmer over high heat. Remove from the heat and transfer the rice mixture to a quarter sheet pan, making sure to spread it evenly in the pan and nestle the chorizo into the rice.