Step 1

In a small bowl, stir together the curry powder, 2 teaspoons salt and ½ teaspoon pepper. Sprinkle the chicken all over with the spice mix, rubbing it into the meat; set aside.

Step 2

In a blender, combine the tomatoes with juices, roasted red peppers, chilies and ginger. Puree until smooth, scraping the jar as needed, about 1 minute; set aside.

Step 3

In a large Dutch oven over medium-high, heat the oil until shimmering. Add the chicken, skin side down, and cook until browned on the bottom, 3 to 4 minutes. Flip the pieces and cook until browned on the second sides, 2 to 3 minutes, then transfer to a large plate and set aside.

Step 4

Return the Dutch oven to medium; add the onion and ¼ teaspoon each salt and pepper. Cook, stirring occasionally, until the onion is softened and golden brown, about 5 minutes. Add the tomato-pepper puree; simmer, uncovered and stirring occasionally, until a spatula leaves a trail when drawn through the mixture, 16 to 20 minutes.

Step 5

Stir in the sweet potatoes (if using), then nestle in the chicken and pour in the accumulated juices. Bring to a simmer over medium-high, then cover, reduce to medium-low and cook, stirring and turning the chicken occasionally, until a skewer inserted into the largest chicken piece meets no resistance and the sweet potatoes are tender (if used), 35 to 40 minutes. Off heat, taste and season with salt and pepper.