Wipe out the saucepan and heat the olive oil in it. Add the shallots and cook over moderate heat until softened, about 4 minutes. Add the tomatoes and chopped beets, season with salt and pepper and cook, stirring occasionally, until the tomatoes release their juices, about 5 minutes. Add the 1 teaspoon of cumin and cook, stirring, until fragrant, about 1 minute. Stir in the vegetable stock and tomato paste and bring to a boil. Cover and simmer over low heat for 10 minutes.