Briefly heating spices and dried chiles in oil or ghee allows their flavors to bloom, creating a flavorful tadka that serves as the backbone of this dish. It also adds a crispy, spicy finish to the creamy mixture of mung beans, lentils, and pigeon peas.
Stir together moong dal, masoor dal, toor dal, salt, turmeric, and 6 cups water in a large saucepan; bring to a boil over medium-high. Reduce heat to medium-low; partially cover, and cook, stirring occasionally, until dal is soft and tender, 35 to 40 minutes. Add up to remaining 1 cup water, 1/4 cup at a time, until desired thickness and consistency is reached.
Stir together atta, 3/4 cup water, and salt in a medium bowl. Knead mixture in bowl until all dry flour is incorporated,adding remaining 1/4 cup water, 1 tablespoon at a time, if needed to incorporate flour. Transfer dough to a clean work surface; knead until stretchy and slightly sticky, 5 to 7 minutes. Shape dough into a ball, and return to bowl. Cover with a clean towel; let stand at room temperature until dough is smooth and matte, about 30 minutes.
Heat oil in a medium-size heavy-bottomed saucepan over medium. Add cardamom, cloves, and cumin; cook, stirring constantly, until fragrant, 30 to 45 seconds. Add onion and serrano chiles; cook, stirring often, until onion is lightly browned around edges, 5 to 8 minutes. Add tomato; cook, stirring often, until tomato begins to break down, 2 to 4 minutes. Remove from heat. Add tomato mixture and cilantro to dal mixture; stir to combine. Season to taste with salt. Cover and keep warm over low.
In a small skillet, heat ghee over medium-high. Add dried chiles and cumin to pan; cook, stirring occasionally, until cumin is toasted and fragrant, about 30 seconds. Divide dal mixture among bowls, and drizzle each portion with desired amount of warm tadka. Sprinkle with additional cilantro, and serve alongside hot roti.