In a large pot, add chickpeas and enough water to cover. Stir in baking soda and soak at least 6 hours or overnight. Drain well and rinse until the water runs clear.
Return the chickpeas to the pot. Add 6 cups cold water, then bring to a boil over medium-high heat.
Reduce heat to medium and simmer until the chickpeas are cooked and softened, about 30 minutes to 45 minutes. Skim any foam off the top of the water with a spoon. Add more water to cover as needed.
In a large saucepan over medium heat, heat oil until shimmering. Add onions and cumin seeds. Cook until the onions have softened and caramelized, about 15 minutes, stirring occasionally.
Stir in ginger, garlic, chili, and a pinch of salt until fragrant, about 1 minute. Stir in the tomatoes and tomato paste and mash to break up the whole tomatoes. Cook until the juice has started to evaporate and the sauce is thick, about 10 minutes.
Stir in the garam masala, ground cumin, chili powder, turmeric, and 1 teaspoon salt. Cook for 2 minutes, then stir in the cooked chickpeas. Garnish with cilantro and serve with fresh vegetables and naan bread.
Notes
Chickpeas: Or substitute 2 (14-oz.) cans chickpeas, rinsed and drained, and omit the baking soda.
Baking soda: Adding baking soda to the bowl while soaking whole and split chickpeas helps soften their skins. They cook faster, have a softer texture, and are easier to digest.
Ginger: Store the whole root ginger in the freezer (peeled or unpeeled) for up to 4 months and grate it as needed using a box grater or microplane grater. To peel the ginger, scrape of the skin with the tip of a spoon or a vegetable peeler.
Green chilies: Look for long, slim "Indian" or "finger" chilis. Or, substitute serranos or even jalapeños. For a milder flavor, remove the seeds.
Garam masala: Find this Indian spice blend at the store, or make your own garam masala with 2 Tbsp. ground cinnamon, 1 Tbsp. freshly ground black pepper, 2 tsp. ground cloves, 1 tsp. ground cardamom, and 1 tsp. ground ginger.
Red chili powder: A single or blend of ground chilies, not the Americanized "chili powder" used in chili recipes. Kashmiri and Guntur chilies are popular varieties, or substitute cayenne pepper.
Yield: This recipe makes about 6 c. of Chana Masala, enough for 4 servings, 1 ½ c. each.
Storage: Store leftovers covered in the refrigerator for up to 4 days.