Heat a medium cast-iron skillet. Add the shallots, garlic and chiles and cook over moderate heat for 3 minutes, stirring occasionally. Add the scallion pieces and cook, stirring occasionally, until everything is charred in spots, about 3 minutes longer. Transfer the contents of the skillet to a large mortar and pound to a coarse paste. Add the chopped tomatoes and pound until incorporated. Stir in the chopped scallion and cilantro and season with salt.