Toast cumin and fennel seeds in a dry heavy skillet over moderate heat, stirring until fragrant and a shade or two darker. Or, toast in a shallow baking pan in a 350 degrees F oven, 5 to 10 minutes. Coarsely crush using a mortar and pestle or an electric coffee/spice grinder.
Whisk tamarind concentrate into hot water until dissolved, then whisk in honey (to taste), oil, salt, and pepper until blended.
Add tomatoes and spices and toss to coat. Let stand at room temperature 1 hour, then season with salt.
Recipe courtesy of Gourmet Magazine