Heat the olive oil in a saucepan over medium-high heat. Add the onions and garlic and cook, stirring, until soft, about 4 minutes. Add the anchovy fillets, olives, and crushed red pepper flakes and cook, stirring often, until the anchovies dissolve, about 2 minutes.
Add the tomatoes, tomato paste, and 1/4 cup water. Stir well. Simmer, uncovered, until the sauce has thickened, about 20 minutes.
Add the parsley and cilantro, and season with salt and pepper. Serve hot.
Yield: about 2 1/2 cups