4 large sweet onions, preferably Walla Walla
6 cloves garlic
1½" piece ginger, peeled
7 tbsp. canola oil
5 tbsp. tomato paste
1 tbsp. ground coriander
1 tbsp. ground cumin
½ tsp. ground turmeric
½ tsp. cayenne pepper
¼ cup yogurt
6 whole, peeled canned tomatoes, drained and crushed
1 (3–4-lb.) chicken, cut into 6–8 pieces, skin removed
Kosher salt, to taste
½ tsp. garam masala
1 tbsp. chopped cilantro
3 serrano chiles, quartered
Cooked basmati rice, for serving