4 cups chopped yellow onions (3 onions)
1/8 cup good olive oil, plus extra for chicken
1/8 cup minced garlic (2 cloves)
2 red bell peppers, cored, seeded, and large-diced
2 yellow bell peppers, cored, seeded, and large-diced
1 teaspoon chili powder
1 teaspoon ground cumin
1/4 teaspoon dried red pepper flakes, or to taste
1/4 teaspoon cayenne pepper, or to taste
2 teaspoons kosher salt, plus more for chicken
2 (28-ounce) cans whole peeled plum tomatoes in puree, undrained
1/4 cup minced fresh basil leaves
4 split chicken breasts, bone in, skin on
Freshly ground black pepper
Chopped onions, corn chips, grated cheddar, sour cream